Rex Thorpe

Professor Rex Thorpe


Professor of Chemical Engineering
MEng, PhD, FIChemE, CEng, FHEA
+44 (0)1483 689270
20 BC 02
9 - 5.30

Academic and research departments

Department of Chemical and Process Engineering.

Biography

University roles and responsibilities

  • Undergraduate Admissions Tutor

Previous roles

2008 - 2015
Head of Chemical and Process Engineering
University of Surrey

Research

Research interests

Courses I teach on

Undergraduate

Supervision

Postgraduate research supervision

Completed postgraduate research projects I have supervised

My publications

Highlights

Gear M, J Sadhukhan, R Thorpe, R Clift, J Seville, M Keast (2018) A life cycle assessment data analysis toolkit for the design of novel processes - a case study for a thermal cracking process for mixed plastic waste, Journal of Cleaner Production, 180, 735-747. https://doi.org/10.1016/j.jclepro.2018.01.015

Thorpe RB, Brampton B, Robson S, Perrault A. (2017) Investigating the effect of an alternative feedstock on the performance of sludge powered generators: developing a theoretical model and analysing trial data. International Water Association Proceedings of The IWA Specialist Conference On Sludge Management: Sludgetech 2017, Imperial College, London, UK.

Kajero, O.T., R B. Thorpe, T. Chen, Wang B., Yao, Y (2016) Kriging meta-model assisted calibration of computational fluid dynamics models, AIChEJ, 62, 4308-4320.   DOI: 10.1002/aic.15352

 

Aliff Radzuan, M.R., M.A. Abia-Biteo Belope, R.B. Thorpe (2016) Removal of Fine Oil Droplets from Oil-in-Water Mixtures by Dissolved Air Flotation, Chemical Engineering Research and Design,115, 19-33.  http://dx.doi.org/10.1016/j.cherd.2016.09.013

Publications

Zigan S, Thorpe Rex, Tuzun U, Enstad GG (2007) Air current segregation of alumina powder, PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION 24 (2) pp. 124-135 WILEY-V C H VERLAG GMBH
Mahood HB, Sharif AO, Thorpe RB (2014) Transient volumetric heat transfer coefficient prediction of a three-phase direct contact condenser, Heat and Mass Transfer/Waerme- und Stoffuebertragung 51 (2) pp. 165-170
© 2014, Springer-Verlag Berlin Heidelberg.An experimental investigation for the time dependent volumetric heat transfer coefficient of the bubbles type, three-phase direct contact condenser has been carried out utilising a short column (70 cm in total height and 4 cm inner diameter). A 47 cm active height was chosen with five different mass flow rate ratios and three different initial dispersed phase temperatures. Vapour pentane and constant temperature tap water as dispersed and continuous phases were implemented. The results showed that the volumetric heat transfer coefficient decreases with increased time until it almost reaches its steady state conditions. A sharp decrease in the volumetric heat transfer coefficient was found at the beginning of the operation and, diminished over a short time interval. Furthermore, a positive effect of the mass flow rate ratios on the volumetric heat transfer coefficient was noted and this was more pronounced at the beginning of the operation. On the other hand, the volumetric heat transfer coefficient decreased with an increase in the continuous phase mass flow rate and there was no considerable effect of the initial dispersed phase temperatures, which confirms that latent heat transfer is dominant in the process.
Min J, Li X, Gao Z, Xiao S, Smith J, Thorpe R (2007) Experimental and CFD studies of a fluid flow in a draft-tube stirred tank, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 40 (8) pp. 630-635 SOC CHEMICAL ENG JAPAN
The velocity distribution and circulation flow rate in a draft-tube stirred tank of 0.8 m diameter were studied experimentally and were numerically simulated using the FLUENT6.2 computational fluid dynamics (CFD) package. A renormalization group (RNG) º-µ turbulent model and multiple reference frame (MRF) were used in the simulation. The circulation flow number and liquid velocity predicted by CFD were in good agreement with experimental values. Both experimental and simulation results show that the axial velocity is far larger than radial and tangential velocities inside and outside the draft tube, and there is a secondary circulation zone close to the outside wall of the draft tube, which could affect the efficiency of the tank. The results are to be of reference for the industrial stirred tank with a draft tube. Copyright © 2007 The Society of Chemical Engineers, Japan.
Harris A, Davidson J, Thorpe R (2002) The Prediction of Particle Cluster Properties in the Near Wall Region of a Vertical Riser, Powder Technology 127 pp. 128-143
Mahood H, Campbell A, Thorpe R, Sharif A (2015) A new model for the drag coefficient of a swarm of condensing vapour-liquid bubbles in a third immiscible liquid phase, CHEMICAL ENGINEERING SCIENCE 131 pp. 76-83 PERGAMON-ELSEVIER SCIENCE LTD
A semi-analytical model for the drag coefficient of a swarm of two-phase bubbles, condensing in direct contact with an immiscible sub-cooled liquid, has been developed. The analysis used a cellular model configuration, assuming potential (but not inviscid) flow around the reference two-phase bubble in the cell. The effect of the condensation ratio within the two-phase bubbles was included using an approximate relation. The drag coefficient for a wide range of Reynolds numbers (0.1. d. Re. d. 1000) has been found using the viscous dissipation integral method, and the effect of the liquid content within the two-phase bubble or the half opening angle (²), and the system void fraction (±) were examined. The drag coefficient has been found to increase with the condensation ratio and with the void fraction of the system. The present model agrees well with previously available experimental data and theoretical predictions for single bubbles or particles.
Daar E, King L, Nisbet A, Thorpe R, Bradley D (2010) Viscosity changes in hyaluronic acid: Irradiation and rheological studies, APPLIED RADIATION AND ISOTOPES 68 (4-5) pp. 746-750 PERGAMON-ELSEVIER SCIENCE LTD
Tay BL, Thorpe RB (2014) Hydrodynamic forces acting on pipe bends in gas-liquid slug flow, Chemical Engineering Research and Design 92 (5) pp. 812-825
In this paper, a one-dimensional, transient theoretical model, the Piston Flow Model (PFM), based on momentum analysis, is proposed to predict the time dependent forces acting on horizontal pipe bends in slug flow. Our experimental apparatus is described and results there from are presented. The PFM has been validated by comparing its predictions with our experimental results for air-water slug flow. The pressure traces, force traces and maximum force predicted agree well with our measurements. © 2013 The Institution of Chemical Engineers.
Watson R, Thorpe R, Davidson J (2012) Vertical plug-flow pneumatic conveying from a fluidised bed, Powder Technology 224 pp. 155-161
Experiments are described on the pneumatic conveying of 2.7mm alumina particles up a vertical riser of internal diameter 46.4mm or 71.4mm. The particles entered the riser from a fluidised bed, via a short horizontal pipe and a bend of radius 75mm. Measured variables included solids flow rates, air flow rates, inlet and outlet air pressures P 1 and P 2, and the pressure profile in the riser. The solids flow rate was consistent with some earlier models of similar systems, in which the plugs of packed solids move up at a velocity of about U-U mf, where U=superficial air velocity and U mf=incipient fluidising velocity. Solids-wall friction is significant and suppresses fluidisation. To model the system approximately, a conveying efficiency=(power for air compression)/(rate of gain of potential energy of solids) is defined and correlated against solids flux. It was found that the conveying efficiency tended to an asymptote just above 20%. The correlation led to a tentative design formula, Eq. (6), for predicting P 1-P 2 at a given solids flow rate. P 1-P 2 is typically between 50% and 100% of the pressure drop needed to support a column of solids of height equal to that of the riser.It was concluded that plug flow pneumatic conveying is a satisfactory technology for transporting coarse particles which cannot be conveyed in leaner regimes due to the possibility of pipeline erosion or solids attrition. © 2012 Elsevier B.V.
Bao Y, Hao Z, Gao Z, Shi L, Smith J, Thorpe R (2006) Gas dispersion and solid suspension in a three-phase stirred tank with multiple impellers, CHEMICAL ENGINEERING COMMUNICATIONS 193 (7) pp. 801-825 TAYLOR & FRANCIS INC
Aliff Radzuan M, Abia-Biteo Belope M, Thorpe RB (2016) Removal of Fine Oil Droplets from Oil-in-Water Mixtures by Dissolved Air Flotation, Chemical Engineering Research and Design 115 (A) pp. 19-33
Dissolved air flotation (DAF) is often used after a primary gravity separator to enhance the quality of wastewater, so it can be released to streams, rivers or the sea. The main aim of the DAF experiments reported here was to measure the oil droplet removal efficiency, (·) mostly in the range 15-80 ¼m from oil-in-water mixtures. The DAF tank used in this investigation was a scale model of real DAF unit. Two kinds of oil, vegetable and mineral and two types of water, fresh and salty were used, and four other operating parameters were varied. A droplet counting and oil-in-water measuring methods were used to estimate the ·. Dimensional analysis concluded that the · in this experiment is a function of eight other dimensionless groups and the experimental data has been subjected to multivariable linear regression. The resulting correlation was found to have a root mean square error of 6.0%, but predict · outside the range zero and one. An alternative mathematical formulation was devised that cannot predict · outside the range. Regression of the data by this formulation, which had the same number of adjustable parameters as the linear regression, was successful with a lower root mean square error of 5.5%.
Li Z, Gao Z, Smith J, Thorpe R (2007) Large eddy simulation of flow fields in vessels stirred by dual rushton impeller agitators, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 40 (8) pp. 684-691 SOC CHEMICAL ENG JAPAN
Thorpe R, Mills N, Pearce P, kirkby N (2011) The influence of heat balance on the economics of advanced anaerobic digestion proceses, 16th European Biosolids and Organic Resources Conference Proceedings Aqua Enviro Technology Transfer
Mahood H, Sharif A, Al-Aibi S, Hawkins D, Thorpe R (2014) Analytical solution and experimental measurements for temperature distribution prediction of three-phase direct-contact condenser, ENERGY 67 pp. 538-547 PERGAMON-ELSEVIER SCIENCE LTD
An experimental and analytical investigation for the temperature distribution prediction of a three-phase bubble-type direct-contact condenser conducted, using a short Perspex column with 4 cm internal diameter and 70 cm height as a direct contact condenser. Vapour pentane and water were exploited as dispersed phase and continuous phase respectively. The effect of mass flow rate ratio (43.69%, 22.97%, 12.23%, 8.61% and 6.46%) and initial dispersed phase temperature (37.6 °C, 38.4 °C and 41.7 °C) on the direct contact condenser output were studied. Linear temperature distributions along direct contact condensers were found experimentally, except at mass flow rate ratio 43.69% and with less magnitude at 22.97%, for different initial vapour temperatures, while theoretically this behaviour is purely linear. The results showed that the mass flow rate ratio and the hold up have a dominant effect on the direct contact condenser output. On the other hand, the initial vapour temperature had a slight effect on the direct contact condenser output temperature which indicates that the latent heat is controlled in the exchange process. The analytical model is based on the one-dimensional mass and energy equations. New expressions for average heat transfer coefficient and two-phase bubbles relative velocity are derived implicitly. Furthermore, the model correlated very well against experimental data obtained. © 2013 Elsevier Ltd.
Tan K, Thorpe R, Zhao Z (2011) On predicting mantle mushroom plumes, Geoscience Frontiers 2 (2) pp. 223-235
Mahood H, Sharif A, Al-Ailbi S, Hossini S, Thorpe R (2016) HEAT TRANSFER MODELLING OF TWO-PHASE BUBBLES SWARM CONDENSING IN THREE-PHASE DIRECT-CONTACT CONDENSER, THERMAL SCIENCE 20 (1) pp. 143-153 VINCA INST NUCLEAR SCI
Woods J, Thorpe R, Johnson S (2008) Horizontal pneumatic conveying from a fluidized bed, CHEMICAL ENGINEERING SCIENCE 63 (7) pp. 1741-1760 PERGAMON-ELSEVIER SCIENCE LTD
Mahood H, Sharif A, Thorpe R (2015) Transient volumetric heat transfer coefficient prediction of a three-phase direct contact condenser, HEAT AND MASS TRANSFER 51 (2) pp. 165-170 SPRINGER
An experimental investigation for the time dependent volumetric heat transfer coefficient of the bubbles type, three-phase direct contact condenser has been carried out utilising a short column (70 cm in total height and 4 cm inner diameter). A 47 cm active height was chosen with five different mass flow rate ratios and three different initial dispersed phase temperatures. Vapour pentane and constant temperature tap water as dispersed and continuous phases were implemented. The results showed that the volumetric heat transfer coefficient decreases with increased time until it almost reaches its steady state conditions. A sharp decrease in the volumetric heat transfer coefficient was found at the beginning of the operation and, diminished over a short time interval. Furthermore, a positive effect of the mass flow rate ratios on the volumetric heat transfer coefficient was noted and this was more pronounced at the beginning of the operation. On the other hand, the volumetric heat transfer coefficient decreased with an increase in the continuous phase mass flow rate and there was no considerable effect of the initial dispersed phase temperatures, which confirms that latent heat transfer is dominant in the process. © 2014 Springer-Verlag Berlin Heidelberg.
Mills N, Pearce P, Farrow J, Thorpe RB, Kirkby NF (2014) Environmental & economic life cycle assessment of current & future sewage sludge to energy technologies, Waste Management 34 (1) pp. 185-195
The UK Water Industry currently generates approximately 800. GW. h pa of electrical energy from sewage sludge. Traditionally energy recovery from sewage sludge features Anaerobic Digestion (AD) with biogas utilisation in combined heat and power (CHP) systems. However, the industry is evolving and a number of developments that extract more energy from sludge are either being implemented or are nearing full scale demonstration. This study compared five technology configurations: 1 - conventional AD with CHP, 2 - Thermal Hydrolysis Process (THP) AD with CHP, 3 - THP AD with bio-methane grid injection, 4 - THP AD with CHP followed by drying of digested sludge for solid fuel production, 5 - THP AD followed by drying, pyrolysis of the digested sludge and use of the both the biogas and the pyrolysis gas in a CHP.The economic and environmental Life Cycle Assessment (LCA) found that both the post AD drying options performed well but the option used to create a solid fuel to displace coal (configuration 4) was the most sustainable solution economically and environmentally, closely followed by the pyrolysis configuration (5). Application of THP improves the financial and environmental performance compared with conventional AD. Producing bio-methane for grid injection (configuration 3) is attractive financially but has the worst environmental impact of all the scenarios, suggesting that the current UK financial incentive policy for bio-methane is not driving best environmental practice. It is clear that new and improving processes and technologies are enabling significant opportunities for further energy recovery from sludge; LCA provides tools for determining the best overall options for particular situations and allows innovation resources and investment to be focused accordingly. © 2013 The Authors.
Thorpe R (2002) Research not flagging, TCE (732) pp. 70-70 INST CHEMICAL ENGINEERS
Hutcheson P, Chew J, Thorpe R, Young C, Regan N (2009) MODELLING OF LIQUID LEAKAGE SPRAYS IN CROSSFLOW, PROCEEDINGS OF THE ASME TURBO EXPO 2009, VOL 3, PTS A AND B pp. 1183-1195 AMER SOC MECHANICAL ENGINEERS
Hau J, Ray R, Thorpe R, Azapagic A (2008) A thermodynamic model of the outputs of gasification of solid waste, International Journal of Chemical Reactor Engineering 6 (1) ARTN A35
Thorpe R, Zigan S, Tuzun U (2009) Characterisation of free-flowing particle jets into storage silos using particle image velocimetry and DEM simulations, Bulk Solids & Powder Science & Technology 2 pp. 55-60 Trans Tech Publications
Bao Y, Gao Z, Huang X, Shi L, Smith J, Thorpe R (2007) Gas-liquid dispersion with buoyant particles in a hot-sparged stirred tank, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 46 (20) pp. 6605-6611 AMER CHEMICAL SOC
van der Meer E, Thorpe R, Davidson J (2000) Flow Patterns in the Square Cross-Section Riser of a Circulating Fluidized Bed and the Effect of Riser Exit Design, Chemical Engineering Science 55 pp. 4079-4099
An experimental investigation of heat exchange in a three-phase direct contact condenser was carried out using a 70-cm-high Perspex tube with a 4-cm inner diameter. The active direct contact condenser comprised 48 cm. Pentane vapour at three initial temperatures (40?,43.5?, and 47.5?) and water at a constant temperature (19?) were used as the dispersed and continuous phases, respectively, with different mass flow rate ratios. The results showed that the continuous phase outlet temperature increased with increasing mass flow rate ratio. On the contrary, the continuous phase temperature decreased with increases in the continuous mass flow rate. The initial temperature of the dispersed phase slightly affected the direct contact condenser output, which confirms a latent phase effect in this type of heat exchanger.
Ray R, Thorpe R (2007) A comparison of gasification with pyrolysis for the recycling of plastic containing wastes, INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING 5 ARTN A85 BERKELEY ELECTRONIC PRESS
Abia-Biteo Belope M, Thorpe R (2007) Alba field three phase separator performance, 13th International Conference on Multiphase Production Technology pp. 399-412
The performance of a particular type of horizontal three phase separator (bucket & weir) was evaluated on the Alba Field, situated offshore of the coast of Equatorial Guinea, by coding a set of equations for the design of the separators. Output parameters such as the oil and water residence times, liquid droplet settling/rising times, minimum lengths for gas-liquid disengagement, and holdup and surge times for the oil bucket and the water compartment, were checked regularly against max/min values for good operation. Thus it was possible to assess the likely behavior of the four Alba field separators to changes in operating variables while also comparing the results obtained from the equations with real field data for performance. The performance of the separators was fairly consistent, even though oils of varying viscosity and temperature were processed. The values of parameters at which performance deteriorated was somewhat different from those usually quoted in the literature for good operation. © BHR Group 2007 Multiphase Production Technology 13.
In this paper, the resultant hydrodynamic force (
FR
, where
2 2
FR = Fx + Fy
) acting on
pipe bends will be discussed. A hypothesis that the peak (resultant) forces,
FR, peak
acting
on pipe bends can be described by the normal distribution function will be tested, with the
purpose of predicting the mean of the
FR, peak
(
FR, mean
) and the standard deviations of the
FR, peak
(
FR, standard deviation
) generated. This in turn allows prediction of the probability of
the largest forces that occasionally occur at various flow rates. This information is vital in
designing an appropriate support for the piping system, to cater the maximum force over a
long period of operation. Besides, this information is also important in selecting a pipe
material or material for connections suitable to withstand fatigue failure, by reference to
the S-N curves of materials. In many cases, large numbers of response cycles may
accumulate over the life of the structure. By knowing the force distribution, ?cumulative
damage? can also be determined; ?cumulative damage? is another phenomenon that can
cause fatigue, apart from the reversal maximum force.
Zigan S, Thorpe Rex, Tuzun U, Gisle GE (2006) Air current segregation of alumina powder, AIChE Annual Meeting, Conference Proceedings
This paper outlines the industrial problem of air current segregation in alumina storage silos which occurs with the handling of the feedstock alumina in aluminium plants. One significant parameter, the air extraction rate, was studied in an experimental silo which was manufactured for this purpose. The experiments conducted in small scale devices displayed the interaction between the particle flow and air current segregation. Results from these experiments show that the increase of the silo air extraction rate reduces air current segregation. The dimensional analysis method has been applied to form dimensionless groups out of the significant parameters. Five dimensionless groups were obtained which is unwieldy. To reduce the number of dimensionless groups the physical properties were lumped into the terminal velocity. This simplified approach gives three dimensionless groups. Initial experiments justify further research to establish weather the simplified approach can scale the dynamic of the flow and the degree of segregation from a small scale silo to industrial equipment.
Mahood HB, Sharif AO, Al-Aibi S, Hawkins D, Thorpe R (2014) Analytical solution and experimental measurements for temperature distribution prediction of three-phase direct-contact condenser, Energy 67 pp. 538-547
An experimental and analytical investigation for the temperature distribution prediction of a three-phase bubble-type direct-contact condenser conducted, using a short Perspex column with 4cm internal diameter and 70cm height as a direct contact condenser. Vapour pentane and water were exploited as dispersed phase and continuous phase respectively. The effect of mass flow rate ratio (43.69%, 22.97%, 12.23%, 8.61% and 6.46%) and initial dispersed phase temperature (37.6°C, 38.4°C and 41.7°C) on the direct contact condenser output were studied. Linear temperature distributions along direct contact condensers were found experimentally, except at mass flow rate ratio 43.69% and with less magnitude at 22.97%, for different initial vapour temperatures, while theoretically this behaviour is purely linear. The results showed that the mass flow rate ratio and the hold up have a dominant effect on the direct contact condenser output. On the other hand, the initial vapour temperature had a slight effect on the direct contact condenser output temperature which indicates that the latent heat is controlled in the exchange process. The analytical model is based on the one-dimensional mass and energy equations. New expressions for average heat transfer coefficient and two-phase bubbles relative velocity are derived implicitly. Furthermore, the model correlated very well against experimental data obtained. © 2013 Elsevier Ltd.
Tay B, Thorpe R (2014) Hydrodynamic forces acting on pipe bends in gas-liquid slug flow, CHEMICAL ENGINEERING RESEARCH & DESIGN 92 (5) pp. 812-825 INST CHEMICAL ENGINEERS
In this paper, a one-dimensional, transient theoretical model, the Piston Flow Model (PFM), based on momentum analysis, is proposed to predict the time dependent forces acting on horizontal pipe bends in slug flow. Our experimental apparatus is described and results there from are presented. The PFM has been validated by comparing its predictions with our experimental results for air-water slug flow. The pressure traces, force traces and maximum force predicted agree well with our measurements. © 2013 The Institution of Chemical Engineers.
Mahood H, Thorpe R, Campbell A, Sharif A (2015) Effect of Various Parameters on the Temperature Measurements In a Three-Phase Direct Contact Condenser, International Journal of Thermal Technologies 5 (1) pp. 23-27
Thorpe R (2001) Kirchhoff no proof, TCE (725) pp. 49-49 INST CHEMICAL ENGINEERS
Hutcheson P, Chew J, Thorpe R, Young C (2008) ASSESSMENT OF MODELS FOR LIQUID JET BREAKUP, PROCEEDINGS OF THE ASME TURBO EXPO 2008, VOL 4, PTS A AND B pp. 1517-1529 AMER SOC MECHANICAL ENGINEERS
Tan K, Thorpe R (2011) Onset of instability of impulsely starting rotating cylinder, AIP Proceedings of the Sixth International Conference on Fluid Mechanics 1376 pp. 104-107
Zigan S, Thorpe R, Tuzun U, Enstad G, Battistin F (2008) Theoretical and experimental testing of a scaling rule for air current segregation of alumina powder in cylindrical silos, POWDER TECHNOLOGY 183 (1) pp. 133-145 ELSEVIER SCIENCE SA
Bao Y, Gao Z, Li Z, Bai D, Smith J, Thorpe R (2008) Solid suspension in a boiling stirred tank with radial flow turbines, IND ENG CHEM RES 47 (7) pp. 2420-2427 AMER CHEMICAL SOC
Kajero OT, Thorpe RB, Chen T (2016) Kriging meta-model assisted calibration of computational fluid dynamics models, AIChE Journal 62 (12) pp. 4308-4320 Wiley
Computational fluid dynamics (CFD) is a simulation technique widely used in chemical and process engineering applications. However, computation has become a bottleneck when calibration of CFD models with experimental data (also known as model parameter estimation) is needed. In this research, the kriging meta-modelling approach (also termed Gaussian process) was coupled with expected improvement (EI) to address this challenge. A new EI measure was developed for the sum of squared errors (SSE) which conforms to a generalised chi-square distribution and hence existing normal distribution-based EI measures are not applicable. The new EI measure is to suggest the CFD model parameter to simulate with, hence minimising SSE and improving match between simulation and experiments. The usefulness of the developed method was demonstrated through a case study of a single-phase flow in both a straight-type and a convergent-divergent-type annular jet pump, where a single model parameter was calibrated with experimental data.
Mahood H, Campbell A, Thorpe R, Sharif A (2017) Measuring the overall volumetric heat transfer coefficient in a vapour-liquid-liquid three-phase direct contact heat exchanger, Heat Transfer Engineering 39 (3) pp. 208-216 Taylor & Francis
An experimental investigation of the volumetric heat transfer coefficient in a three-phase direct contact condenser was carried out. A 75-cm long cylindrical Perspex column with a 4 cm diameter was used. Only 48 cm of the column was utilised as the active direct contact condensation height. Pentane vapour at three different initial temperatures (40°C, 43.5°C and 47.5°C), with differing mass flow rates, and tap water at a constant initial temperature (19°C) with five different mass flow rates were employed as the dispersed phase and the continuous phases, respectively. The results showed that the volumetric heat transfer coefficient increased with increasing mass flow rate ratio (variable dispersed phase mass flow rate per constant continuous phase mass flow rate), the continuous phase mass flow rate and holdup ratio. An optimal value of the continuous phase mass flow rate is shown for an individual dispersed phase mass flow rates. This value increases with increasing vapour (dispersed) phase mass flow rate. Furthermore, it was observed that the initial driving temperature difference had no effect on the volumetric heat transfer coefficient. While, the temperature gained by the continuous phase has a considerable effect.
Thorpe RB, Brampton B, Robson S, Perrault A (2017) Investigating the effect of an alternative feedstock on the performance of sludge powered generators: developing a theoretical model and analysing trial data, Proceedings of The IWA Specialist Conference On Sludge Management: Sludgetech 2017 International Water Association
Trials performed by Thames Water on a Sludge Powered Generator (SPG) have used sludge from a Thermal Hydrolysis Process (THP) as feed. Data from the trials with THP product sludge at Thames Water's Crossness SPGs was subject to data analysis by converting the trial data into flows of operating cost. Sludge is a mixture of many chemicals and these would be very time consuming to analyse for combustion performance in full detail. Therefore sludge has been simplified to a mixture of water and a single combustible chemical component (coniferyl alcohol) with the same heat of combustion as water-free sludge and roughly the right elemental analysis. This simplification enables the thermal behaviour of the combustion, including its tendency to extinguish without support fuel, to be captured. Both the simplified model and the data analysis from the trial show the THP product sludge is a viable fuel which produces a net financial benefit to the SPG?s operation.
Co-produced water re-injection is a mature recovery technique for oil fields. Co-produced water that is not re-injected is the largest wastage stream in the oil industry. Handling, treatment and management (especially re-injection back into the reservoir) is an expensive operation. PWRI is a secondary oil recovery method with a small recovery factor in the range of 15-25% and contributes to many surface and subsurface issues, e.g., scaling and reservoir plugging, resulting in the decline of water injectivity, and thus lower oil recovery. This reduction, of course, impinges significantly on the revenue stream of major oil corporations.
However, low-salinity (LowSal) water injection is an emerging method that boosts oil recovery by reducing the downsides of produced water re-injection. Using forward osmosis to produce low-salinity water for injection is a novel idea, in which the co-produced water will be the draw solution. In this concept, low-salinity water from water wells (brackish water) is used as the feed to dilute the co-produced water. The diluted co-produced water will then be re-injected as LowSal water. The obviously cheaper alternative of direct dilution of the co-produced water with the brackish water might not produce a water compatible with the oil reservoir in both ionic composition and strength.
Data have been collected from different oil fields with various co-produced water and formation characteristics. Different co-produced water treatments were observed in each oil field due to differences in co-produced water chemistry. The water sample for analysis was taken at the skim tanks prior to the water injection stage.
A theoretical resistance-in-series model for the forward osmosis stage is presented, which has been adapted from the literature, which incorporates the mass transfer equations, in which the boundary layer and thin-film theory for the membrane intrinsic layers are integrated. An improved shell mass transfer correlation is introduced in addition to the incorporation of a modified reflection coefficient into the resistance-in-series model. The collected data were then incorporated into the theoretical model to calculate and evaluate the forward osmosis performance and, in turn, the water chemistry before re-injection.
A forward osmosis rig has been erected to use the latest hollow fibre membrane supplied by the Toyobo Company (Japan). Water and solute flux were measured to validate the model estimations. The model estimated
Mahood Hameed B., Campbell Alasdair, Baqir Ali Sh., Sharif Adel, Thorpe Rex (2017) Convective Heat Transfer Measurements in a Vapour-Liquid-Liquid Three-Phase Direct Contact Heat Exchanger, Heat and Mass Transfer 54 (6) pp. 1697-1705 Springer Verlag
Energy usage is increasing around the world due to the continued development of technology, and population growth. Solar energy is a promising low-grade energy resource that can be harvested and utilised in different applications, such solar heater systems, which are used in both domestic and industrial settings. However, the implementation of an efficient energy conversion system or heat exchanger would enhance such low-grade energy processes. The direct contact heat exchanger could be the right choice due to its ability to efficiently transfer significant amounts of heat, simple design, and low cost. In this work, the heat transfer associated with the direct contact condensation of pentane vapour bubbles in a three-phase direct contact condenser is investigated experimentally. Such a condenser could be used in a cycle with a solar water heater and heat recovery systems. The experiments on the steady state operation of the three-phase direct contact condenser were carried out using a short Perspex tube of 70 cm in total height and an internal diameter of 4 cm. Only a height of 48 cm was active as the direct contact condenser. Pentane vapour, (the dispersed phase) with three different initial temperatures (40?,43.5? and 47.5?) was directly contacted with water (the continuous phase) at 19?. The experimental results showed that the total heat transfer rate per unit volume along the direct contact condenser gradually decreased upon moving higher up the condenser. Additionally, the heat transfer rate increases with increasing mass flow rate ratio, but no significant effect on the heat transfer rate of varying the initial temperature of the dispersed phase was seen. Furthermore, both the outlet temperature of the continuous phase and the void fraction were positively correlated with the total heat transfer rate per unit volume, with no considerable effect of the initial temperature difference between the dispersed and continuous phases.
Gear Matthew, Sadhukhan Jhuma, Thorpe Rex, Clift Roland, Seville Jonathan, Keast M (2018) A life cycle assessment data analysis toolkit for the design of novel processes - A case study for a thermal cracking process for mixed plastic waste, Journal of Cleaner Production 180 pp. 735-747 Elsevier
The earlier in the development of a process a design change is made, the lower the cost and the higher the impact on the final performance. This applies equally to environmental and technical performance, but in practice the environmental aspects often receive less attention. To maximise sustainability, it is important to review all of these aspects through each stage, not just after the design. Tools that integrate environmental goals into the design process would enable the design of more environmentally friendly processes at a lower cost. This paper brings together approaches based on Life Cycle Assessment (LCA) including comparisons of design changes, hotspot analysis, identification of key impact categories, environmental break-even analysis, and decision analysis using ternary diagrams that give detailed guidance for design while not requiring high quality data. The tools include hotspot analysis to reveal which unit operations dominate the impacts and therefore should be the focus of further detailed process development. This approach enables the best variants to be identified so that the basic design can be improved to reduce all significant environmental impacts. The tools are illustrated by a case study on the development of a novel process with several variants: thermal cracking of mixed plastic waste to produce a heavy hydrocarbon product that can displace crude oil, naphtha, or refinery wax or be used as a fuel. The results justified continuing with the development by confirming that the novel process is likely to be a better environmental option than landfill or incineration. The general approach embodied in the toolkit should be applicable in the development of any new process, particularly one producing multiple products.
Mahood H, Campbell A, Sharif A, Thorpe R (2016) Heat Transfer Measurement in a Three-Phase Direct-Contact Condenser under Flooding Conditions, Applied Thermal Engineering 95 pp. 106-114 Elsevier
The transient temperature distribution and volumetric heat transfer coefficient during the 16 inception of flooding in a three-phase bubble type direct contact condenser have been 17 experimentally investigated. The flooding mechanism and the factors affecting the onset of 18 flooding of the three-phase direct contact column are not considered. A short Perspex column 19 of 70 cm total height and 4 cm internal diameter utilising two immiscible fluids was studied. 20 Pentane vapour with initial temperatures of 40°C, 43.5°C and 47.5? was the dispersed phase 21 and tap water at a constant temperature (19?) was the continuous phase. Only 48 cm of the 22 column was used as the active height and different mass flow rates of both phases were used. 23 The experimental results showed that the instantaneous temperature distribution along the 24 direct contact column tends to be uniform when the direct contact column is working under 25 flooding conditions. Furthermore, the volumetric heat transfer coefficient increases as the 26 dispersed mass flow rate is increased towards the flooding limit and remains constant along 27 the column height. In addition, the dispersed phase mass flow rate that leads to flooding 28 increased with increasing mass flow rate of the continuous phase. The initial temperature of 29 the dispersed phase did not have a considerable effect on the flooding inception limit under 30 the present experimental conditions
Kajero OT, Thorpe Rex, Yao Y, Wong DSH, Chen Tao (2017) Meta-model based calibration and sensitivity studies of CFD simulation of jet pumps, Chemical Engineering & Technology 40 (9) pp. 1674-1684 Wiley
Calibration and sensitivity studies in the computational fluid dynamics (CFD) simulation of process equipment such as the annular jet pump are useful for design, analysis and optimisation. The use of CFD for such purposes is computationally intensive. Hence, in this study, an alternative approach using kriging-based meta-models was utilised. Calibration via the adjustment of two turbulent model parameters, C_¼ and C_2µ, and likewise two parameters in the simulation correlation for C_¼ was considered; while sensitivity studies were based on C_¼ as input. The meta-model based calibration aids exploration of different parameter combinations. Computational time was also reduced with kriging-assisted sensitivity studies which explored effect of different C_¼ values on pressure distribution.
The UK Water Industry currently generates approximately 800GWh pa of electrical energy from sewage sludge. Traditionally energy recovery from sewage sludge features Anaerobic Digestion (AD) with biogas utilisation in combined heat and power (CHP) systems. However, the industry is evolving and a number of developments that extract more energy from sludge are either being implemented or are nearing full scale demonstration. This study compared five technology configurations: 1 - conventional AD with CHP, 2 - Thermal Hydrolysis Process (THP) AD with CHP, 3 - THP AD with bio-methane grid injection, 4 - THP AD with CHP followed by drying of digested sludge for solid fuel production, 5 - THP AD followed by drying, pyrolysis of the digested sludge and use of the both the biogas and the pyrolysis gas in a CHP. The economic and environmental Life Cycle Assessment (LCA) found that both the post AD drying options performed well but the option used to create a solid fuel to displace coal (configuration 4) was the most sustainable solution economically and environmentally, closely followed by the pyrolysis configuration (5). Application of THP improves the financial and environmental performance compared with conventional AD. Producing bio-methane for grid injection (configuration 3) is attractive financially but has the worst environmental impact of all the scenarios, suggesting that the current UK financial incentive policy for bio-methane is not driving best environmental practice. It is clear that new and improving processes and technologies are enabling significant opportunities for further energy recovery from sludge; LCA provides tools for determining the best overall options for particular situations and allows innovation resources and investment to be focused accordingly.
Mahood H, Campbell A, Thorpe R, Sharif A (2015) Heat Transfer Efficiency and Capital Cost Evaluation of a Three-Phase Direct Contact Heat Exchanger for the Utilisation of Low-Grade Energy Sources, Energy Conversion and Management 106 pp. 101-109 Elsevier
Low-grade energy cycles for power generation require efficient heat transfer equipment.
Using a three-phase direct contact heat exchanger instead of a surface type exchanger, such
as a shell and tube heat exchanger, potentially makes the process more efficient and
economic. This is because of its ability to work with a very low temperature driving force, as
well as its low cost of construction. In this study, an experimental investigation of the heat
transfer efficiency, and hence cost, of a three-phase direct contact condenser has been carried
out utilising a short Perspex tube of 70 cm total height and 4 cm internal diameter. Only 48
cm was used for the direct contact condensation. Pentane vapour with three different initial
temperatures (40?, 43.5? and 47.5?) was contacted with water with an inlet temperature
of 19?. In line with previous studies, the ratio of the fluid flow rates was shown to have a
controlling effect on the exchanger. Specifically, the heat transfer efficiency increased
virtually linearly with this ratio, with higher efficiencies also being observed with higher flow
2
rates of the continuous phase. The effect of the initial temperature of the dispersed phase was
shown to have a lower order impact than flow rate ratio. The capital cost of the direct contact
condenser was estimated and it was found to be less than the corresponding surface
condenser (shell and tube condenser) by 30 times. An optimum value of the continuous phase
flow rate was observed at which the cost of the condenser is at a minimum.
Keywords: Three-phase direct contact condenser, heat transfer efficiency, costing
Sempere F., Winter P., Waalkens A., Hühnert N., Cranshaw I., Beigi B., Thorpe R. B. (2018) Treatment of discontinuous emission of sewage sludge odours by a full scale biotrickling filter with an activated carbon polishing unit, Water Science and Technology 77 (10) pp. 2482-2490 IWA Publishing
A SULPHUS" biotrickling filter (BTF) and an ACTUS" polishing activated carbon filter (ACF) were used at a wastewater treatment plant to treat 2,432 m3·h?1 of air extracted from sewage sludge processes. The project is part of Thames Water?s strategy to reduce customer odour impact and, in this case, is designed to achieve a maximum discharge concentration of 1,000 ouE·m?3. The odour and hydrogen sulphide concentration in the input air was more influenced by the operation of the sludge holding tank mixers than by ambient temperature. Phosphorous was found to be limiting the performance of the BTF during peak conditions, hence requiring additional nutrient supply. Olfactometry and pollutant measurements demonstrated that during the high rate of change of intermittent odour concentrations the ACF was required to reach compliant stack values. The two stage unit outperformed design criteria, with 139 ouE·m?3 measured after 11 months of operation. At peak conditions and even at very low temperatures, the nutrient addition increased considerably the performance of the BTF extending the time before activated carbon replacement over the one year design time. During baseline operation the BTF achieved values between 266-1,647 ouE·m?3 even during a 6 days irrigation failure of the biofilm.
It is well accepted that the technical, financial and environmental performance of a chemical process is largely determined during design. Therefore, the development of tools that integrate environmental considerations would enable the design of more environmentally friendly processes at a lower cost. This research investigates how Life Cycle Assessment (LCA) can be applied at any stage in the design process to produce useful information for design, not just after the plant is operating, which is the norm for LCA. The tools have been applied to the development of a novel process (the RT7000): thermal cracking of mixed plastic waste to produce several hydrocarbon products with the potential to displace crude oil, naphtha, or refinery wax or be used as a fuel.

To allow LCA to guide the design process, a toolkit methodology was developed including comparisons of design changes, hotspot analysis, identification of key impact categories, environmental break-even analysis, and decision analysis using ternary diagrams. The results of applying these tools justified continuing with the development by confirming that the novel process is likely to be a better environmental option than landfill or incineration.

At the later stages of design, advanced tools such as process simulations become attractive and allow a more accurate estimation of material and energy flows. A simulation of the RT7000 in Aspen Plus® was developed that provided data for a wide range of feed compositions. The RT7000 continued to have lower environmental impact to incineration offering a saving equivalent to 969-1305 kgCO2/tonne plastic processed. It was also ascertained that variation in feed composition does influence environmental performance, but not enough to affect the outcomes of decision making.

The general approaches used in this work to assess the RT7000 should be applicable to the development of any new process. Benefits and insights similar to those obtained in the case study can realistically be expected when these methodologies are applied to any new processes. Therefore the results have been published in the Journal of Cleaner Production (Gear et al., 2018)

Dissolved air flotation (DAF) is a separation technique, often used after a primary gravity separator to enhance the quality of the wastewater, so it can be released to streams, rivers, and the sea in a manner not to violate the environment. DAF works by removing oil droplets from oil-in-water mixtures by air bubbles of an average diameter of 50 ¼m with a standard deviation of 5.5 ¼m. The air bubbles used in these experiments were generated as a result of rapid pressure reduction of water saturated with air when it released from the bottom of the DAF tank. The main aim of the DAF experiments reported here was to measure the removal efficiency of oil droplet mostly in a diameter range between 15 and 80 ¼m that were created using a static mixer. The DAF tank located at the University of Surrey was a scale model of existing DAF unit used by Thames Water plc. The effects of seven operating parameters that are believed to affect the performance of DAF were investigated. The operating parameters consist of inlet oil concentration, air saturator pressure, temperature, the salinity of continuous phase, type of oil, flow rate of the mixture and coagulant dosage. Two independent analysis methods were used to estimate the removal efficiency of oil droplet. They are a droplet counting and an oil-in-water measuring methods. The droplet counting method used a Coulter Counter that provided numbers of oil droplet passed through the aperture based on the selected size range. The oil-in-water measuring method used an ultraviolet and visible spectroscopy (UV-Vis), which the removal efficiencies were estimated from the absorbance values that were measured at the optimum wavelength of 400 nm. The analyses done with these two methods found that the inlet oil concentration and flow rate of the mixture into DAF tank were inversely proportional to the oil droplet removal efficiency. The other parameters such as saturator pressure, temperature, water salinity and alum dosage were directly proportional to the oil droplet removal efficiency. Vegetable oil, which has larger spreading coefficient than lamp oil obtained a better oil droplet removal efficiency. Coulter Counter showed that a better removal efficiency for vegetable oil obtained at larger oil droplet ranges size, 50¼m and above. This was because the oil droplets were removed by gravity and enhanced by air bubbles. Contrary to lamp oil, which the worst removal efficiency was obtained at larger size ranges due to the coalescence of oil droplets. Results from these experiments were used to obtain a correlation that can predict removal efficiency. This was done by performing dimensional analysis. It was carried out using Buckingham Pi and scaling methods. It involved with the identification of two non-dimension and nine dimensional parameters. The dimensional analysis concluded that the removal efficiency is a function of eight other dimensionless groups, which are ratio of inlet oil and mixture flow rate
Beigi B.H.M., Thorpe R.B., Ouki S., Winter P., Waalkens A. (2019) Hydrogen Sulphide and VOC Removal in Biotrickling Filters: Comparison of Data from a Full-scale, Low-emission Unit with Kinetic Models, CHEMICAL ENGINEERING SCIENCE PERGAMON-ELSEVIER SCIENCE LTD

In this paper, data is published on the removal of H2S and VOCs by a Biotrickling Filter (BTF) demonstration plant, namely a SULPHUS", which was installed by Thames Water in late 2015. These data, along with some data already published by Sempere et al. (2018), were compared to the predictions of a number of existing and novel models for the removal of a single pollutant by a biofilm.

The two widely used models of Ottengraf and van den Over (1983) were found to be inadequate with sum of squares of errors of 11 and 41 mg2m-6 respectively. These models are based on zero-order kinetics in the biofilm which according to the M-M kinetic model, are likely to be inaccurate at low pollutant concentration. The odour control unit was designed to produce low emission levels of less than 1 ppmv of H2S, rendering the zero-order assumption unlikely to be accurate. A model based on first-order kinetics, which also has some support in the literature, was found to be a better, but not a good, fit to the data with a sum of squares of errors of 4.7 mg2m-6. A novel model for the BTF based on M-M kinetics was found to be a good fit to the shape of the data with the lowest sum of squares of errors of 2.5 mg2m-6. This novel M-M model was also identified as the best fit for VOC data from the same unit. Other publications support the M-M approach with a product of saturation constant and Henry?s Law constant of about 50 mg m-3, which is equivalent to an H2S level in the gas phase of about 40 ppmv. Broad agreement was found between the SULPHUS", experiments and data in the literature for other BTFs destroying H2S under the zero-order regime, at V_max value of about 0.3 g/m3/s. This paper represents an attempt to harmonise a literature that was previously disparate, which has not previously been attempted.