S. Devotta

Thermodynamic design data for absorption heat pump systems operating on water-lithium bromide part II: Heating

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 presented for water-lithium bromide absorption systems for heating. The interactions of operating temperatures have been illustrated graphically.

Comparison of theoretical Rankine power cycle performance data for 24 working fluids

Abstract The boiling temperature T BO in a Rankine cycle power plant is largely determined by the temperature of the available heat supply. The gross temperature drop ( T BO − T CO ) 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 η R and the pressure ratio ( PR ) are determined automatically. The only way that the values of η R and ( PR ) can be varied is to choose another working fluid. Of the 24 working fluids for which comprehensive thermodynamic data are available, only 18 have critical temperatures high enough to be considered for use in Rankine cycle power plants with a boiling temperature of 120°C and only seven can be considered for a boiling temperature of 200°C. Values of η R are listed for gross temperature drops of 20, 30, 40, 50, 60 and 70 K for boiling temperatures of 80, 100, 120, 160 and 200°C respectively.

A study of economiser performance in a water-lithium bromide absorption cooler

Abstract 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.

The economics of heat pump assisted distillation systems—Part 4. Experimental assessment with methanol-water mixtures

Abstract 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.

Steady- and dynamic-state simulations of heat-pumps. Part II: Modelling of a motor driven water-to-water heat-pump

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 section and a superheating section. The compression has been assumed to be polytropic and the expansion isenthalpic.

The economics of heat pump assisted distillation systems III—a comparative analysis on three alcohol mixtures

Abstract 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 economically attractive when payback period (PBP) is the main economic criterion. For typical conditions considered (PBP) values are 2 yr for the methanol-ethanol system, 2.6 yr for the ethanol-water system and 5 yr for the methanol-water system. For acceptable economic conditions, Rankine heat pump effectiveness factor (HPE) R of the system should be at least 0.5, and the running time should be more than 5000 h yr −1 . The reflux ration has little influence on the economics of the heat pump assisted distillation system.

The economics of heat pump assisted distillation systems—II. Analysis of ethanol-water mixtures

Abstract 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 period is adopted as the criterion, has been assessed. Results has been presented in graphical form to illustrate the optimum conditions for economic viability.

Steady- and dynamic-state simulations of heat-pumps. Part I: Literature review

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.

Derived thermodynamic design data for heat pump systems operating on R290

Abstract The theoretical Rankine coefficient of performance and the compression ratios have been presented for heat pump systems operating on R290. These values are listed in tabular form for temperature lifts of 10–75°C and for condensing temperatures of 15–85°C in 5°C increments. Several graphs have been drawn to illustrate the feasible operating range for R290 heat pump systems. These derived thermodynamic data can be used for the rapid preliminary design of heat pump systems operating on R290.

Operating characteristics of a water-to-water mechanical vapour compression heat pump using R114: Part I—Interaction between dependent and independent parameters

Abstract 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 to evaporator. The effect of the variations of these independent parameters on the dependent parameters including condensing temperature, condenser load, compressor load and coefficient of performance are presented.