Single Stage Absorption Heat Transformer Research Articles

00/00588 Productivity trends in India's energy intensive industries

A single stage absorption heat transformer (SAHT) is analyzed with the aid of a graphical exergy methodology based on energy-utilization diagrams (EUDs). This analysis provides detailed information on internal phenomena such as the driving forces and the distribution of the exergy loss in each subsystem. Two cases with different flow ratios are investigated. They show that the exergy loss in the premixing process in the absorber is very large. To reduce that exergy loss, a multiple-compartment absorber in close-to-equilibrium operation is proposed. This scheme can give high temperature for useful heat even when a low flow ratio is applied.

Graphical exergy study on single stage absorption heat transformer

A single stage absorption heat transformer (SAHT) is analyzed with the aid of a graphical exergy methodology based on energy-utilization diagrams (EUDs). This analysis provides detailed information on internal phenomena such as the driving forces and the distribution of the exergy loss in each subsystem. Two cases with different flow ratios are investigated. They show that the exergy loss in the premixing process in the absorber is very large. To reduce that exergy loss, a multiple-compartment absorber in close-to-equilibrium operation is proposed. This scheme can give high temperature for useful heat even when a low flow ratio is applied.

Heat transformation with the ternary working fluid TFE-H 2O-E181 : Transformation de chaleur avec le fluide de travail ternaire TFE-H 2O-E181

As shown in previous papers, the binary mixture of trifluoroethanol (TFE) and tetraethylene-glycoldimethylether (E181) seems to be advantageous for absorption heat pumps and absorption heat transformers. Both substances are completely miscible and applicable in a wide temperature range from below 0 up to 160°C. The density of TFE vapour is much higher than that of water, so that condenser and evaporator become smaller than in processes with water as a working substance. Because of the fairly low thermal conductivity and the low enthalpy of evaporation of TFE it is, however, advantageous to use TFE-water instead of pure TFE with E181 as working substances. The present paper deals with the thermophysical properties of this ternary mixture. The thermal stability, vapour-liquid equilibrium, density and viscosity were measured. The enthalpy of the ternary mixture was predicted from data for the three binary subsystems. As a study of the single-stage absorption heat transformer shows, up to 15 mass% or almost 50 mol% of TFE in the mixture TFE-E181 can be replaced by water. The COP of a process working with the ternary mixture is slightly higher than that of a process working with the binary mixture TFE-E181. Because of the higher thermal conductivity and enthalpy of evaporation of TFE-water compared with pure TFE, the heat transfer is improved. Also, the costs for the mixture are reduced.

Coupling a single-stage absorption heat transformer with finite heat sources/sinks

The coupling between a single-stage heat transformer and finite heat sources and sinks is considered. A simple lumped-parameter mathematical model shows that the performance is noticeably reduced in comparison with the simpler case of an infinite (constant temperature) heat source. The best performance is obtained when the evaporator and the generator are fed in series, the evaporator being placed upstream.

Feasibility Study of Ammonia-Water Vapor Absorption Heat Transformer

Many industrial sectors reject heat to the atmosphere in the form of hot water with a temperature between 40° and 70°C. This low grade heat can be upgraded by using a vapor absorption heat transformer (AHT). The present study considers a single stage AHT with binary mixture of NH3–H2O as the working fluid. The performance characteristics of the system have been evaluated by solving the governing mass and energy balance equations using a digital computer. It is found that the permissible range of concentration across the absorber is 0.04<ΔX<0.075 for the following operating conditions: Tusefulheat≤120°C,43°≤Twasteheat≤88°Cand10°≤Tsink≤27°C.

Heat transformer cycles—II. Thermodynamic analysis and optimization of a single-stage absorption heat transformer

In the present paper the results of a detailed analysis of a real one-stage absorption heat transformer working with ammonia-water are discussed. Irreversibilities due to temperature differences, pressure drops and efficiencies for the absorber and the liquid pumps are taken into account and also the performance of the rectification column is considered. Heat fluxes are delivered or removed by fluids like water or humid air. The working temperatures of the process are varied. From the analysis losses of exergy are detected and an exergy flow diagram of the whole process is presented.