IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Vapour ejector refrigeration system yields better performance when the ejector operates at choking-mode. A computer code based on existing one dimensional ejector theory has been developed to carry out a study on performance of the system. When operating conditions are changed, the critical performance parameters of the system get shifted to different critical values. The code includes effects of change in specific heat of the working fluid and friction at the constant-area mixing chamber besides internal irreversibility of the ejector. The simulated performance results are compared with the available experimental data from the literature for validation. The effects of operational parameters and ejector configurations of the system on critical performance are studied. Also, comparison of performance of the system with environment friendly refrigerants, R134a, R152a, R290, R600a and R717 is made. © 2004 Elsevier SAS. All rights reserved.

Department of Mechanical Engineering

International Journal of Thermal Sciences

Analysis of a vapour ejector refrigeration system with environment friendly refrigerants

Fibre-reinforced plastic (FRP) flat plate collector (FPC) with single cover can be used for augmenting evaporation of water in tannery effluent. In this paper, experimental studies on FRP - FPC is presented. The performance is compared with the theoretically simulated performance. The evaporation rate increases, with increase in insolation and wind speed and decrease in relative humidity, concentration and mass flow rate. © 2003 Elsevier Ltd. All rights reserved.

Applied Thermal Engineering

Analysis of a single cover FRP flat plate collector for treating tannery effluent

The objective of this work is to analyze a system for evaporating the water in tannery effluent (soak liquor). This system is designed based on the principle of forced convective evaporation. Soak liquor is made to flow as a thin film and air is drawn against the falling liquor film. This facilitates the direct contact heat and mass trasfer between liquor and air. The system is modeled by applying the energy and mass balance. A parametric study has been carried out to find out the effect of operating parameters on the rate of evaporation. An experimental setup has been constructed and experiments have been conducted which prove the viability of the system. Theoretical performance matches closely with that of experiments. It is shown that the proposed forced convective evaporation system is better than existing methods of evaporation of tannery effluent in terms of evaporation rate as well as area requirement. © 2003 Elsevier Science ltd.

International Communications in Heat and Mass Transfer

Analysis of forced convective evaporation system for tannery effluent (soak liquor)

In this paper, comparison between theoretical and experimental anaylis of an open type flat collector for tannery effluent treatment is presented. Effect of the parameters like insolation, wind speed, relative humidity, mass flow rate and salt concentration on the evaporation rate of water in the effluent is studied. An open type fibre reinforced plastic (FRP) flat plate solar collector is used for experimentation. The evaporation rate increases for increase in insolation, wind speed and mass flow rate and decrease in relative humidity and concentration. © 2003 Elsevier Science Ltd.

Comparison between simulated and experimental performance of an open solar flat plate collector for treating tannery effluent

A computer simulation of a vapour jet refrigeration system is carried out using a one-dimensional model based on mass, momentum and energy balances. The simulated performance of the system is in good agreement with the available experimental performance from the literature. A comparison of system performance is carried out for the same ejector geometry using the environmentally friendly working fluids R123, R134a, R152a and R717 (ammonia). The results suggest that, for different boiler temperatures, the entrainment ratio and the system efficiency (COP) depend mainly on the ejector geometry and the compression ratio.

Performance comparison of vapour jet refrigeration system with environment friendly working fluids

Experiments are carried out on a bubble absorber, operating as part of a vapour absorption refrigeration system working with HCFC22-DMF to obtain heat and mass transfer and pressure drop data. The results are evaluated to obtain the dependence of absorption process on different parameters. Experimental data are compared with the numerical correlation relating Sherwood number, Reynolds number, Schmidt number and length to diameter ratio developed earlier by the authors. Also the experimental pressure drop is compared with the pressure drop obtained from other well known classical correlations and the numerical model.Experiments are carried out on a bubble absorber, operating as part of a vapour absorption refrigeration system working with HCFC22-DMF to obtain heat and mass transfer and pressure drop data. The results are evaluated to obtain the dependence of absorption process on different parameters. Experimental data are compared with the numerical correlation relating Sherwood number, Reynolds number, Schmidt number and length to diameter ratio developed earlier by the authors. Also the experimental pressure drop is compared with the pressure drop obtained from other well known classical correlations and the numerical model.

Experiments on a bubble absorber

International Journal of Numerical Methods for Heat and Fluid Flow

Finite element analysis of a bubble absorber

A model of the absorption process in a vertical tubular bubble absorber working with R22-DMF, R22-DMA, R22-DMETEG, R22-DMEDEG and R22-NMP is developed using finite element method employing Galerkin's technique. The objective of this paper is to study the influence of the liquid and gas properties on the volumetric mass transfer coefficient. Analysis have also been done using ammonia-water as working fluid, the results obtained are compared with those in the literature and the agreement is found to be good. A correlation for mass transfer coefficient is proposed as a function of Reynolds number, Schmidt number and length to diameter ratio. The correlation can be used either in estimating the mass transfer rates or in fixing up any of the major design parameters namely length required for complete absorption and diameter.

Heat and Mass Transfer/Waerme- und Stoffuebertragung

Analysis of a bubble absorber working with R22 and five organic absorbents

An analysis of the thermodynamic cycle for a two stage intermittent solar refrigerator is performed for R22-DMF, R22-NMP and R22-DMETEG. The effects of different parameters, like volume ratio, and high and low pressure stage initial concentrations on cycle performance are studied for these combinations. The comparison of cycle performances between these working fluids helps in selecting the best working fluid combination.

Energy Conversion and Management

Comparative study of cycle performance for a two stage intermittent solar refrigerator working with r22-absorbent combinations

A vapour absorption refrigeration system (VARS) in which a transfer tank replaces the conventional solution pump is analysed. Six fluid pairs with R22 as the refrigerant and different absorbents: DMA; DMF; DMETEG; DMETrEG; DMEDEG; and NMP are considered. Variations in COP, circulation ratio, percent mass of generated vapour utilised for transfer-tank operation, and minimum generator temperature are compared over a wide range of operating conditions. In general, R22-DMA, R22-DMF, and R22-DMETrEG are preferable for a transfer-tank operated VARS. At high generator temperatures or low condenser temperatures, R22-DMA gives the best overall performance. When the temperatures of the evaporator, absorber, and condenser are high, one may prefer R22-DMF as the working fluid. © 1995.

GENERAL

Renewable Energy

Performance of different working fluids in transfer-tank operated vapour absorption refrigeration systems

In this paper the viscosity and thermal conductivity of both the liquid and vapour for the refrigerants R152a and R142b have been estimated and presented. Available properties of liquid thermal conductivity of R142b and R152a and the liquid viscosity of R152a are compared with the estimated values. It is found that the agreement is good. Transport properties of R142b, which is a potential replacement for R114 in medium temperature heat pump applications, is compared with that of R114. Also, the properties of R152a, which is considered as a possible replacement of R12 in refrigeration and low‐temperature heat pump applications, is compared with the properties of the other possible replacement of R134a. Copyright © 1994 John Wiley & Sons, Ltd.

International Journal of Energy Research

Estimation of viscosity and thermal conductivity of R142b and R152a

A thermodynamic analysis of a single-stage vapour absorption refrigeration system operating with a transfer tank is presented with R22-DMF as working fluid. The effects of generator, condenser and evaporator temperatures on performance parameters such as circulation ratio, percentage of generated vapour consumed by transfer tank and coefficient of performance are presented. Also, its performance is compared with the conventional continuous absorption refrigeration system. The transfer-tank-operated system may be preferred when the difference between condenser and evaporator temperatures is less than about 25°C. © 1994.

Analysis of an absorption refrigeration system with transfer tank

In this paper, analysis of an open type flat plate collector for tannery effluent treatment is presented. The effects of parameters like orientation of collector, film thickness, insolation, ambient temperature and relative humidity on the effluent evaporation rate are studied. It is found that the collector facing south at an inclination of 12.68° and having a solution film thickness of 5 mm gives maximum year round performance. The performance of this open type flat plate collector is compared with that of the conventional pond. © 1994.

Analysis of an open type flat plate collector for tannery effluent treatment

The performance of flat-plate collectors serving as low- and high-pressure generators in a two-stage intermittent solar refrigeration system is predicted from transient heat-transfer analysis. Experimental results obtained with a laboratory, two-stage solar refrigerator are presented and compared with theoretical predictions. The agreement is found to be good. © 1991.

Energy

Theoretical and experimental investigations of generators in a two-stage solar refrigerator

The operation of a two-stage intermittent solar refrigerator is explained briefly with the help of schematic and cycle diagrams. Experiments have been conducted on a laboratory unit, fabricated using flat-plate collectors of 6 m2 exposed area. The experimental results are presented through graphs and Tables. The results are compared with those predicted by heat transfer analysis of the collector and the thermodynamic analysis of the cycle. The agreement between the two is found to be good. It has been possible to produce ice at low generation temperatures, using the two-stage system. Ice produced is 1.5-2 kg/m2 collector area.

World University root node

SESI Journal

Experimental investigations on a two-stage intermittent solar refrigeration system

The paper explains briefly the operations of a single stage and a two stage ammonia-water intermittent solar refrigeration system with the help of relevant schematic and cycle diagrams. The performances of these two systems are compared based on the results of the thermodynamic analyses of the corresponding cycles. It is inferred that a stage system is capable of producing the required refrigeration with relatively high overall coefficient of performance at even low generation temperatures. Hence, it is a viable refrigeration system, especially when flat collectors are used for the collection of solar energy. © 1989.

Solar and Wind Technology

Comparison of performances of single stage and two stage intermittent ammonia-water solar refrigeration systems

A two stage intermittent solar refrigeration system is described briefly. In such a system, when flat-plate collectors are used for generation, it is very likely that the two generation temperatures are around the same value. The successful operation of the cycle under such conditions depends upon the proper selection of the initial solution concentrations in the high and low pressure generators and the volume ratio of the generators. These parameters have been evaluated with the help of the thermodynamic analysis of the refrigeration cycle operating with ammonia as the refrigerant and water as the absorbent. © 1986.

A two stage intermittent solar refrigeration system-Evaluation of salient parameters

This paper refers briefly to the operation of a single stage system with the help of a cycle diagram. Such a system, using flat plate collector for generation, is likely to fail at certain operational parameters. The paper then discusses the operation of a two stage system with the help of schematic and cycle diagrams. The relations that are used in predicting the system performance are also given.