An experimental study of a two-phase closed loop thermosyphon with dual evaporator in parallel arrangement

A Two-phase Closed Loop Thermosyphon (TCLT) has been applied to many industrial fields as a waste heat recovery system, a telecommunication cooling system and other heat transport devices for the last 2 decades. It is common to design a TCL T to consist of one evaporator, one condenser and 2 separated lines of condensate liquid and vapor of working fluid. The present study was conducted in search of the new possibility of connecting multiple evaporators in parallel to the evaporator section. There has been little information about this so far. It is expected that a TCL T with multi-evaporator would provide a new solution to designing a compact telecommunication cooling system where lots of heat generating circuit boards are connected in parallel arrangement. In the present study a TCL T with two evaporators was prepared and given to a series of operational performance tests. The study was focused on investigating its operational problems and collecting information about its performances. Some important findings are as follows. The main source of operational instability was an occurrence of a hot dried patch on the heated surface when the rate of beat input was raised to a certain limit. For a single evaporator mode of the present TCL T model, the maximum allowable heat transport rate was about 650W. For dual evaporator mode of operation, this instability problem was found to be closely related not only to the quantity of heat flux but also the difference in heat input rate to each evaporator. For all those problems, it was found that a TCL T with multi-evaporator could operate in a proper way when the thermal loads were evenly distributed to all the evaporator or the maximum power gap were contained under about +/- 5 similar to 7% of the average power input.