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