Heat Wheels
Do heat wheels work in tropical climate?
In theory, the concept is simple, but temperature difference alone cannot justify the use of heat wheels in tropical climates. Why?
1. Heat wheels require an specific enthalphy difference significant enough to justify the cooling gained from capturing exhaust air. It also relies on the exhaust volume and the overall cool energy it carries.
2. Heat wheels add pressure drop into the system - i.e. exhaust fan AND supply air fan will consume addtional energy to overcome the friction losses added by the heat wheels . This additional energy is premium electrical energy. Just think - is it worth capturing low heat energy by using more electrical power?
Before a heat wheel is considered in your plant, request the following to be done
1. Plot a simulation on a Psychrometric Chart for various exhaust and outdoor air condition and determine the actual cooling energy saved
2. Calculate the additional kW required to counter the pressure drop of the heat wheel - dont' forget to do it for the supply air fan and exhaust fan! Remember every inch of pressure means kW!
3. Determine the cooling load cost savings due to recovery - i.e. chiller plant kW/ton x Cooling Load Recovered which will determine the kW energy saved
The results from the exercise above will clearly show the potential savings (from recovery) and the additional energy used by higher fan kW.