Using plate and frame heat exchangers to add extra heat or cooling to the system

saves space in the air handler with fewer coils and fewer access doors.

Often, energy recovery alone is not sufficient to condition outside air to the desired supply air temperature. Additional heat or cooling is required.

This can be accomplished either by installing an additional coil in the air handler after the energy recovery coil (video 1), or by installing plate and frame heat exchangers on the hydronic module (video 2 and 3).

Video 1
Video 2
Video 3

To achieve a high energy efficiency, the supplemental heat or cooling needs to be considered when determining the optimal circulation rate of the heat transfer fluid. In a multi-functional system, a pure "performance optimization", that is, controlling the fluid flow rate as a function of only air volume, results in very low efficiency.

Optimal control of a multi-functional energy recovery system needs to take into account all operating conditions including ari volumes, fluid and air temperature, the performance of the plate heat exchangers, and the performance mapping of the coils, pumps and valves. 

Advantages of integral plate and frame heat exchangers

Electrical Energy consumption is lower because air pressure drop is lower

By providing the required supplemental heating and cooling through plate and frame heat exchangers on the hydronic module, the air pressure drop from heating and cooling coils is eliminated. This reduces fan power and fan size which reduces first cost and annual operating expenses.

Shorter air handlers are required because no heating or cooling coils are required

If the german hygiene standard VDI 6022 has to be met even larger savings are possible, as there will be no extra heating or cooling coils in the air handler that require additional service room for cleaning before and after them.