Example Cabinet Cooling Calculation
You are evaluating a 6310 heat exchanger with an Ostro fan for cooling an electronics cabinet. The water entering the heat exchanger is at 20°C and a flow rate of 1 gpm. The heat load, Q, is 2400W.
What is the temperature of cooled air entering the cabinet (i.e. the temperature of air leaving the heat exchanger) and what is maximum temperature in the cabinet (i.e. the temperature of warm air entering the heat exchanger)?
First check the performance curve of 6310 in the catalog. You will see that with a 1gpm water flow and the Ostro fan which supplies approximately 250 cfm, its performance is 80W/°C.
Since we know that Q is 2400W and Q/ITD is 80°C/W, we can calculate Initial Temperature Difference (ITD).
ITD = 2400W ÷ 80°C/W = 30°C
We also know that incoming water temperature is 20°C. We can therefore calculate incoming air temperature:
The incoming air temperature = 20°C + 30°C = 50°C.
To determine outgoing temperature of the air, we use the 'Air Flow' chart using parameters 250 CFM and 2400 W.
We find the change in temperature is approximately 17°C. The outgoing air temperature is 50°C - 17°C = 33°C.
We know that this heat exchanger with the Ostro fan will cool air to 33°C, and the hottest temperature air in the cabinet will reach is 50°C.
To determine the outgoing temperature of water we use the 'Water Flow' chart.
At 1 gpm and 2400 W, this shows that the change in temperature is approximately 9°C. Therefore, the outgoing water temperature is 20°C + 9°C = 29°C.
Graphs for air, water, oil, and EGW are available in downloadable PDF format. These are helpful for sizing heat exchangers and cold plates and are also useful in a variety of other temperature change calculations.