Energy Recovery Modules
for Direct or Indirect-Fired Heating or Cooling Sections
The above depicts how an energy recovery module works with a direct-fired, make-up air handler. The 60% efficient
energy recovery module handles two air streams in a cross-flow pattern: 0° F (-17.8° C) outside air and 70° F (21.1° C)
exhaust air, in this example.
By using exhaust air to heat outside air, air entering the air handler* is 42° F (5.6° C), rather than 0° F (-17.8° C). As a result, less energy is required to heat outside air entering the make-up air handler.
without energy recovery module - 2,268,000 BTU/hr
with energy recovery module - 907,200 BTU/hr
*Formula: energy recovery module efficiency x (exhaust air temperature – outside air temperature) + outside air temperature = air temperature exiting energy recovery module entering air handler
60% [70° F (21.1° C) – 0° F (-17.8° C)] + 0° F (-17.8° C) = 42° F (5.6° C)
**Formula (based on 30,000 CFM unit): 1.08 * 30,000 * (exhaust air temperature – outside air temperature) = BTU/hr
1.08 * 30,000 * [70° F (21.1° C) – 0° F (-17.8° C)] = 2,268,000 BTU/hr
1.08 * 30,000 [70° F (21.1° C) – 42° F (5.6° C)] = 907,200 BTU/hr
The module is constructed of aluminum sheets that form air channels in layers. Half the layers allow air flow in one direction and the other half are orientated perpendicular. As the cool outside air passes through every other channel, warm inside exhaust air is passing through the other channels perpendicular to the outside air. Each aluminum surface is heated by the warmer air and heat is transferred to the cool outside air. The aluminum sheets are corrugated to create turbulence and enhance the heat transfer efficiency.