HA-2469 (RP 140) -- Thermosiphon Loop Performance Characteristics: Part 3. Simulated Performance PDF

This is the fourth of a set of four papers which describe the work carried out at the University of Windsor (l, 2) for ASHRAE under Research Project RP-140, IIDevelopment of Performance Characteristics of Two-Phase Thermosiphon Loops" (3). The first paper (4) deals with condensation in inclined tubes, the second (5) with the experimental study and the third (6) with the development of the computer program used in this study. This program is capable of simulating the performance of any thermosiphon loop such as that shown in Fig. 1.

This paper presents the results of a number of loop simulations which were carried out to illustrate typical behavior of thermosiphon loops as various parameters are changed. The simulation results have been divided into two sets depending upon the nature of the application of the system. The first set of results is for the case where one exchanger is at a lower elevation than the other thereby producing a loop which will transfer heat very well in one direction (source at lower elevation) and very poorly in the other direction (source at higher elevation). Such loops will be referred to as unidirectional. The second set of results is for the case where both heat exchangers are at the same elevation thereby producing a system which works equally well in either direction. Such loops will be referred to as bidirectional.

In order to focus on the performance of the loop itself rather than a specific system, the effect of the exterior heat transfer performance of the evaporator and condenser tubes (due to fins and air flow rates, etc.) was eliminated by specifying the evaporator and condenser tube surface temperatures. Thus the conductances reported represent the internal loop conductance. The reciprocal of this value would represent the resistance to heat flow due to the loop itself.