Experimental and Theoretical Study of Vacuum Cooling System

Abstract

A vacuum cooling system and the parameters which affect on its performancewere studied experimentally and theoretically. For the experimental study the rig wasbuilt up to studying the performance of cooling system in three cases. These casesare: Cooling water by vacuum only, cooling water in conventional method, andcooling water by vacuum with condensation.The experimental results show that the addition of a condenser to the vacuumcooling system leads to sweep of largest amount of generated vapor, also the timeconsumed for the process was decreased. The times required for cooling 45 g fromwater from temperature 29oC to 10oC for the three test cases were 4375 second, 3535second and 263 second, respectively. Vacuum cooling with condenser is a fastcooling of three systems test, which is about (13.7 times) faster than the system ofnatural convection cooling. To work properly, the existence of condenser is veryimportant in vacuum cooling. It normally removes the large amount of water vaporgeneration (about 94%).For the theoretical study, a computer program was built up by employing thegoverning equation to simulate the performance of the vacuum cooling system. Thetheoretical results indicate an acceptable agreement with the experimental results.Also, the results show that the decreasing of condenser temperature causes decreasingof cooling time according to the equation (t = 0.2031Tcd4 - 2.8958 Tcd3 + 16.406Tcd2 - 21.104 Tcd + 313.39), and increasing the evaporation surface area leads todecreasing of cooling time according to the equation (t=1/ (0.0006*Area+0.0005)),and the increasing of water mass causes in increasing of cooling time according to theequation (t=7.2667*mass+14).