MODULE III Air-conditioning and Cooling technology Page 74

Fig. 59 Pressure-temperature diagram for a solar powered cooling model

One can show that the heat quantity diverted in the condenser is usually the same as the heat supplied to the evaporator, and thus, as a result, more or less identical to the heat supplied to the generator. In Fig. 58, the heat quantity absorbed by the evaporator equals 1. The heat 1/0 must then be supplied to the generator. The condenser heat is then identical to that of the evaporator (1), and the absorber heat is the same as that of the generator 1/0. The second main theorem of thermodynamics is again hidden in the heat relationship 0. For the material pair water/lithium bromide it lies between 0.7 and 0.8 and for ammonia/water between 0.4 and 0.6.


The absorption heat transformer
Function principle

The most important components of the circulation process are the same as for the absorption heat pump: the evaporator E, the absorber A, the solution pump SP, the solution heat exchanger SHE, the generator G, the solution expansion valve SEV and the condenser C. Important to note, however, is that the evaporator and absorber now lie at the higher pressure and the generator at the lower. The expansion valve between the condenser and the evaporator must therefore be replaced by a condensate pump CP.
In the evaporator E, the fluid refrigerant will absorb heat Q1', and evaporate from the heat source at the temperature T1. The refrigerant steam will be drawn from the refrigerant poor solution in the absorber and absorbed. The absorption heat Q2 will be passed on to the available heat sink at temperature T2.

The solution which has been enriched by the absorption of refrigerant will have its surface tension reduced to the condenser pressure in the solution expansion valve SEV after it has been cooled by the poor solution coming from the generator. From the expansion valve, the rich solution reaches the generator G. It is there regenerated with the heat Q1" at temperature T1. The expelled refrigerant condenses in the condenser C, the condensation heat Q0 is passed on to the waste heat sink at temperature T0. The condensate is then pumped to the evaporator pressure with the condensate pump CP. The work material circulation process is thereby closed. .