Sukumar Devotta

National Environmental Engineering Research Institute | NEERI ·  Environmental Impact and Risk Assessment Division (NEERI)

India is a large producer and user of chlorofluorocarbons (CFCs) in the refrigeration and air-conditioning (RAC) sector. Government of India has taken several steps to restrict the production and consumption of CFCs. Refrigerant conservation through recovery, recycling (R&R) and reclamation is one way of reducing emissions and encouraging timely ph...

Some selected fluids have been assessed for their suitability as alternatives to HCFC-22 for air conditioners. Only those refrigerants with zero ozone depletion potential are considered. NIST CYCLE_D has been used for the comparative thermodynamic analysis. Among the refrigerants studied (HFC-134a, HC-290, R-407C, R-410A, and three blends of HFC-32...

This is an energy sector case study and it involves Total, Totalgaz, the Senegal government, the European Development Fund, about 50 distribution companies, and local communities. The consumption of fuel wood was leading to deforestation and desertification in Senegal. But the introduction of butane as a household fuel with a suitable energy effici...

The basic objective of the Ecofrig project is to adapt the hydrocarbon technology (HT), developed by German manufacturers, for Indian domestic and commercial refrigeration appliances in cooperation with a few Indian industry and research partners. The project involved a voluntary partnership between the Swiss, German and Indian governments and priv...

This case study, for the energy sector, highlights the technology cooperation between Arun Natural Gas Field (northern Sumatra), Mobil Oil Corporation, and Pertamina, the Indonesian national oil company. The natural gas is produced, liquefied, and shipped to Japan and Korea for use in power plants, displacing the alternative use of coal or heavy oi...

Based on the basic concepts and techniques involved for automatic control of continuous distillation columns for binary systems, a scheme is proposed for the control of distillation column for the ethanol–water system. Using the established norms for the control of mechanical vapor compression heat pumps, a control scheme is proposed for the heat p...

A water chiller with an open reciprocating compressor has been used to comparatively assess the performance of HFC-134a with reference to CFC-12 under as close to identical conditions as possible. Performance characteristics of the chiller under retrofit conditions show that HFC-134a offers better cooling load and coefficients of performance vis-a-...

CFC-11, CFC-12, CFC-114 and HCFC-22 are used as mechanical vapour compression heat pump working fluids for low and high temperature applications. Because of the Montreal Protocol, alternative heat pump working fluids to CFCs have to be identified and developed. This paper discusses the various potential alternatives screened from various families o...

The theoretical performances of some hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and hydrofluorinated ethers (HFEs) have been assessed as alternatives to CFC11 by using the standard refrigeration parameters including pressure ratio, specific compressor displacement and theoretical Rankine coefficient of performance. From this compa...

The theoretical performances of a few selected fluids, screened from about 30 hydrofluorocarbons and fluorinated ethers, have been comparatively assessed for high-temperature working fluids as alternatives to CFC114 by using some basic and derived heat pump parameters for an ideal Rankine cycle including pressure ratio, specific compressor displace...

Prediction of volumetric and thermodynamic data for some refrigerants using their boiling points, and possible also their critical properties as the basic input data, has been attempted using corresponding states and some established equations for various properties for a variety of fluids. The properties predicted include vapour pressure, vapour a...

The current status of HCFC-123 as the alternative to CFC-11 in air-conditioning, refrigeration and heat pump systems is reviewed. The theoretical Rankine coefficient of performance (COP) and the pressure ratios (PR) have been presented for heat pumps operating on HCFC-123. Composite plots between pressure ratio, theoretical Rankine coefficient of p...

The theoretical performance of some HFCs, fluorinated ethers and amine have been comparatively assessed as alternatives to CFC12 by using the standard refrigeration parameters, including pressure ratio, specific compressor displacement, theoretical Rankine coefficient of performance and shaft power per ton of refrigeration. From the energy point of...

HFC134a has been identified as an alternative to CFC12 for refrigeration applications. Significant progress has been made in the use of HFC134a for refrigeration. This paper analyses the suitability of HFC134a along with those of HCFC22, HCFC124, HFC134, HCFC142b and HFC152a as alternatives to CFC12 for heat-pump applications. Some basic and derive...

A composite plot relating evaporating temperature TEV, condensing temperature TCO, pressure ratio (PR) and theoretical Rankine coefficient of performance (COP)RR is presented for HFC134a. The theoretical performance of HFC134a has been comparatively assessed along with HCFC22, HFC134, HFC152a, HCFC124 and HCFC142b as alternatives to CFC12 by using...

For the screening of alternatives of chlorofluorocarbons (CFCs), one of the limitations encountered is the nonavailability of primary data including normal boiling point and critical temperature. The Joback method, which was proposed for the prediction of boiling point from molecular structure of an organic compound, when tested for an aliphatic ha...

There is a considerable scope for mechanical vapour compression (MVR) open cycle heat pumps for energy conservation in ethanol distillation in India. In the proposed MVR heat pump assisted distillation scheme, a freshly treated water stream is preheated, expanded and fed to a falling film evaporator. Low pressure steam is produced by extracting hea...

Performance data have been obtained on a small absorption heat transformer operating with the following working fluid/absorbent pairs: (i) water-lithium bromide, (ii) water-mixture of lithium chloride and lithium bromide (1:1 by weight), and (iii) water-lithium chloride. It is possible to deliver heat at temperatures beyond 100 °C. It is demonstrat...

The performance of an experimental heat-pump-assisted dryer under operating conditions of some practical interest was studied. The system was operated using R11 and R12. The approach velocity of air to the evaporator and the superheat of the working fluid at the exit of the evaporator were identified as the critical parameters for optimization. The...

A mathematical model for an integrated heat-pump-assisted dryer has been developed. The dryer has been modelled considering the heat transfer and simultaneous heat and mass transfer zones. The heat-pump heat exchangers have been modelled by writing the enthalpy balance for differential lengths considering the various zones on the air and working-fl...

A closed-cycle absorption system has been analyzed for simultaneous cooling and heating using water-lithium bromide as the refrigerant-absorbent pair. System performance has been analyzed for condensing temperatures in the range of 35°C to 100°C while keeping the evaporating temperature constant at 5°C and the absorber outlet temperature at 35°C. I...

The mathematical models of the individual components of the heat-pump system presented in Part II have been translated into computer programs. The structures of these for steady- and dynamic-state simulation are presented. The results of the simulation have been compared with some experimentally observed data. The steady-state simulation was found...

This paper describes a mathematical model of a solar regenerator, which could be used in either an open-cycle desiccant-cooling system or an open-cycle absorption-cooling system. The model has been validated by experimental data from the published literature. The effects of the variation of the values of various parameters on the performance of the...

A simplified procedure for estimating the Rankine power cycle efficiency is presented. This procedure does not need any detailed thermodynamic data but requires only the liquid specific heat and the latent heat of vaporization at boiler temperature. This procedure is tested for its application to eight potential Rankine power cycle working fluids f...

Performance data have been obtained on a small absorption cooler operating on the following working pairs: (i) water-lithium chloride and (ii) water-lithium chloride/lithium bromide (1:1 by weight). For a similar range of evaporating temperatures, the water-LiBr/LiCl pair requires lower generator temperature than the water-Lid pair. By comparing th...

Various mathematical models on mechanical vapour-compression heat pumps since 1975 have been reviewed with particular emphasis on their bases and end uses. These models have been classified according to steady- and dynamicstate simulations.

A mathematical model to simulate the steady- and dynamic-state behaviour of an existing water-to-water electric-motor driven heat-pump has been evolved. The condenser area on the working fluid side has been divided into two sections: namely, condensing section and sub-cooling section, while the evaporator area has been divided into an evaporating s...

Various methods of capacity modulation of electric motor driven heat pumps have been reviewed with a particular emphasis on variable-speed motors. The effect on the steady-state performance of the heat pump, of variation in the externally-controllable independent parameters, while the compressor speed or the evaporator heat transfer area was adjust...

Derived thermodynamic design data, including Carnot coefficients of performance, enthalpy based coefficients of performance and flow ratios for possible combinations of operating temperatures, are presented for absorption heat transformers operating on water-lithium chloride. The variations of the derived data with operating temperatures are graphi...

In heat pump assisted distillation, the working fluid can either be one of the components of the mixture to be distilled or it can be an external working fluid. The operating parameters of more than thirty potential heat pump assisted distillation systems have been listed. A detailed assessment can only be made if detailed thermodynamic data are av...

Steady-state performance data have been obtained on a domestic sized engine-driven water-to-water heat pump. The optimum working fluid suction superheat for the system was found to be 12°C. Over a range of heat sink conditions, increasing the engine speed linearly increased the total heat prouduced by the unit. Similarly, over a range of heat sourc...

A heat pump assisted distillation system has been designed for the separation of ethanol from 7 per cent aqueous mixtures to produce 93 per cent ethanol by weight. The distillation column has been designed on the basis of conventional design procedures. Valve trays were chosen to provide operational flexibility. R114 was chosen as the working fluid...

Heat pumps can be incorporated advantageously into processes which require simultaneously both cooling and heating. The economics of heat pumps in India for simultaneous heating and cooling is assessed with respect to process, design and economic parameters. For the typical conditions of various parameters in India, a heat pump system for simultane...

Theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R152a. These values are listed in tabular form for temperature lifts of 10–75°C and condensing temperatures of 20–85°C in 5°C increments. A composite plot has been drawn to illustrate the feasible operating range of R152...

The free choice of operating temperatures in absorption systems is limited by the Gibbs phase rule and the thermodynamic properties of the working pair. Tables of possible combinations of operating temperatures and concentrations, including flow ratios, Carnot coefficients of performance and enthalpy-based coefficients of performance, have been pre...

The free choice of operating temperatures in absorption systems is limited by the Gibbs phase rule and the thermodynamic properties of the working pair. Tables of possible combinations of operating temperatures and concentrations, including flow ratios, Carnot coefficients of performance and enthalpy based coefficients of performance have been pres...

The sensitivity of the economics of heat pump assisted dryers to various factors such as design, operational and economic variables, when payback period is adopted as the criterion, has been assessed for Indian conditions. Results have been presented in graphical form to illustrate the optimum conditions for economic viability. For the specific typ...

Heat pumps have not developed more rapidly in spite of their widely acknowledged potential to recycle and save energy. The primary, but by no means the only, reason is economic: people are far more interested in saving money than in saving energy. Hitherto, relatively undeveloped heat pump systems have had to compete with highly developed alternati...

The boiling temperature TBO in a Rankine cycle power plant is largely determined by the temperature of the available heat supply. The gross temperature drop (TBO − TCO) is largely determined by the temperature of the coolant in the condenser. This means that for a given working fluid, the theoretical Rankine power cycle efficiency ηR and the pressu...

Although the economics of heat pump assisted distillation systems appear to be attractive for certain mixtures, there is no published literature dealing with design and performance data. This work reports some experimental data on heat pump assisted distillation using methanol-water mixtures and demonstrates the attractiveness of the scheme.

The interactions between the independent parameters and the dependent parameters for a specially designed water-to-water heat pump have been studied experimentally. The independent parameters studied were working fluid flow rate, water flow rate to condenser, water flow rate to evaporator, temperature of water to condenser, and temperature of water...

An analysis of the operating characteristics obtained by four different experimentalists over a period of about five years on a water-to-water mechanical vapour compression heat pump was made. The analysis showed that there was no significant difference between the four sets of results. The heat pump used in the study was still in the acceptance re...

The compression ratio (CR) is largely determined by the choice of compressor in a mechanical vapour compression heat pump system. The condensing temperature is largely determined by the required temperature of the heat to be delivered. This means that for a given working fluid, the theoretical Rankine coefficient of performance and the gross temper...

The effectiveness of an economiser heat exchanger in a water-lithium bromide absorption cooler has been shown to decrease with increases in flow ratio and cooling capacity. Experiments have been carried out with six levels of cooling capacity and nine values of flow ratios.

Closed cycle absorption cooling systems have been analysed using water-lithium bromide and ammonia-water as working fluid pairs. An open cycle system using water-lithium bromide has also been analysed and compared with the closed cycle system. A flat plate collector has been considered for heat supply to the generator of the closed cycle systems. T...

Crystallization can cause operating problems in absorption heat pumps and coolers. It is therefore necessary to determine the optimum flow ratio which will avoid crystallization and provide the minimum decrease in coefficient of performance. Experimental data have been obtained for absorber temperatures in the range 35. 2 to 48. 7 degree C. The flo...

New data are reported for the decomposition of R12B1 under dynamic conditions and of R11, R12B1 and R114 in the presence of a polyalphaolefin based synthetic hydrocarbon oil under static conditions. These and some previously reported results are presented graphically; a comparative evaluation of the thermal stability of R11, R12B1, R113 and R114 an...

Heat and mass transfer experiments have been carried out on the Solar Generator of an open cycle cooler with solar simulation. The latter was done first using a radiation source consisting of CSI lamps and they by an electric heater. The working fluid pair was water/lithium chloride. Experimental data on heat and mass transfer have been obtained fo...

Further experiments, using water-lithium bromide as the working pair, have been carried out on an absorption cooler using an auxiliary heat exchanger in addition to an economiser. The size of this auxiliary heat exchanger. which is used to cool the hot solution from the generator prior to its entry into the absorber, is shown to be critical. This a...

The theoretical Rankine power cycle efficiencies ηR and the pressure ratios (PR) have been presented for Rankine power cycles operating on R12B1. These values are listed in tabular form for temperature drops of 10–75°C and boiler temperatures 30–125°C in 5°C increments. A composite graph showing the relationship between ηR, TBO, (PR) and temperatur...

The design and economic model presented previously has been used for a preliminary economic analysis of heat pump assisted distillation of ethanol-water mixtures. The sensitivity of the economics for ethanol-water mixtures to various factors such as selection of heat pump wotking fluid, design, operational and economic variables, when payback perio...

The economics of heat pump assisted distillation of three alcohol mixtures, namely methanol-water, ethanol-water and methanol-ethanol, have been analysed and compared using the economic model outlined in Part 1. The results suggest that, at typical conditions for each system, the system with the smaller column temperature lift is the most economica...

Experiments have been carried out on an existing absorption cooling system operating on water-lithium bromide. Heat losses were reduced and experiments were carried out at very high flow ratios. These experiments show that the generator temperature can be reduced by about 10 degree C for given condenser and evaporator temperatures. These results br...

The theoretical Rankine power cycle efficiencies ηR and the pressure ratios (PR) have been presented for Rankine power cycles operating on R718. These values are listed in tabular form for temperature drops of 10–75°C and for boiler temperatures 100–350°C in 5°C increments. A composite graph showing the relationship between ηR, TBO, (PR) and temper...

The theoretical Rankine power cycle efficiencies and the pressure ratios (PR) have been presented for Rankine power cycles operating on R11. These values are listed in tabular form for temperature drops of 10–75°C and for boiler temperatures 45– 180°C in 5°C increments. A composite graph showing the relationship between , (PR) and temperature drop...

The theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R505. These values are listed in tabular form for temperature lifts of 10–75°C and for condensing temperatures of 15–100°C in 5°C increments. Several graphs have been drawn to illustrate the feasible operating range...

A water to water heat pump specially designed and instrumented for research has been used to determine the actual coefficients of performance of R11 for condensing temperatures in the range 70°C to 104°C. 101 experimental points were obtained and these lie on a smooth curve with a standard deviation of 6.32 per cent. The results are compared with d...

The theoretical Rankine power cycle efficiencies ηR and the pressure ratios (PR) have been presented for Rankine power cycles operating on PP1. These values are listed in tabular form for temperature drops of 10-75°C and for boiler temperatures 45-160°C in 5°C increments. A composite graph showing the relationship between ηR, TBO, (PR) and temperat...

The theoretical Rankine coefficients of performance (COP)R and the compression ratios have been presented for heat pumps operating on R142b. These values are listed in tabular form for temperature lifts of 10-75°C and for condensing temperatures TCO of 15-100°C in 5°C increments. Several graphs have been drawn to illustrate the feasible operating r...

The theoretical Rankine coefficient of performance and the compression ratios have been presented for heat pump systems operating on R717. These values are listed in tabular form for temperature lifts of 10-75°C and condensing temperatures of 15-115°C in 5°C increments. Several graphs have been drawn to illustrate the feasible operating range for R...

The theoretical Rankine coefficients of performance and the compression ratios have been presented for heat pump systems operating on R600. These values are listed in tabular form for temperature lifts of 10-75°C and the condensing temperatures of 10-140°C in 5°C increments. Several graphs have been drawn to illustrate the feasible operating range...

The theoretical Rankine coefficient of performance (COP)R and the compression ratios have been presented for heat pump systems operating on R113. These values are listed in tabular form for temperature lifts of 10–75°C in 5°C increments and condensing temperatures for every degree in the range 15–185°C. Several graphs have been drawn to illustrate...

An experimental heat pump dehumidifier is described. Actual coefficients of performance (COP)A are plotted against the gross temperature lift (TCO - TEV) for various bypass ratios and air velocities. Interpolated values of (COP)A for a specified temperature lift were obtained by fitting each set for various dry bulb temperatures of air leaving the...

Drying is one of the most energy intensive unit operations. In many applications the drying temperatures required are low enough to make the inclusion of a heat pump in the system worthy of consideration. Five drying/dehumidification systems, including three with heat pumps, have been compared theoretically on the basis of specific power consumptio...

Experimental data from the heat pump dehumidifier described in Part II (Tai et al, 1982) are presented in terms of the specific power consumption (SPC). Plots are presented of (SPC) against superheat at the exit of the evaporator for various air bypass ratios and (SPC) against approach velocity of air to the evaporator for various dry bulb temperat...

The design sequence of a heat pump is described. Various design aspects of a heat pump are discussed with reference to individual components of the system.Some of the common refrigerants have been theoretically analysed for their suitability as heat pump working fluids. Rankine coefficients of performance and compression ratios are chosen as the im...

The theoretical Rankine coefficients of performance (COP)R and the compression ratios have been presented for heat pumps operating on R500. These values are listed in tabular form for temperature lifts of 10-75°C in 5°C increments and condensing temperatures TCO for every degree in the range 15-85°C. Several graphs have been drawn to illustrate the...

The theoretical Rankine coefficients of performance (COP)R and the compression ratios have been presented for heat pumps operating on R216. These values are listed in tabular form for temperature lists of 10-75°C and for condensing temperatures of 10-160°C in 5°C increments. Several graphs have been drawn to illustrate the feasible operating range...

Tables of derived thermodynamic data for water, Refrigerant 718, are presented in a form suitable for calculations based on the use of water as the working fluid of a heat pump. The use of the tables of the theoretical Rankine coefficient of performance and of the pressure ratio across the compressor of a heat pump system is illustrated by an examp...

The theoretical Rankine coefficient of performance (COP)R and the compression ratios have been presented for heat pump systems operating on R502. These values are listed in tabular form for temperature lifts of 10–75°C in 5°C increments and condensing temperatures for every degree in the range 15–60°C. Several graphs have been drawn to illustrate t...

The theoretical Rankine coefficients of performance (COP)R and the compression ratios have been presented for heat pump systems operating on R22. These values are listed in tabular form for temperature lifts of 10–75°C in 5°C increments and condensing temperatures TCO for every degree in the range of 15–85°C. Several graphs have been drawn to illus...

This paper presents simulation results for the heat exchangers of an HCFC-22 window air conditioner retrofitted with R-407C. The test conditions are per the Indian Standard IS 1391 (1992) for unitary air conditioners. The simulation was carried out using EVAP-COND, a heat exchanger model developed by NIST. A typical Indian window air conditioner of...