Chapter hvac engineering Fundamentals: Part 1 Introduction

10.17.1
Coil loop heat recovery system
The coil loop or runaround heat recovery system consists of two heat
exchange coils, a pump, and interconnecting piping (Fig. 10.27). The
coils are usually placed in the outside air supply and exhaust air-
streams because this will provide the greatest temperature gradient
and therefore the maximum energy recovery. Sensible heat is trans-
ferred from the exhaust airstream to the outside airstream. Using
eight-row coils, the system will recover up to 50 percent of the total
available sensible heat energy. This is not entirely ‘‘free’’ energy be-
cause additional fan work is required to overcome the air pressure
losses through the coils, and pump energy is required.
The three-way control valve is used to keep the exhaust air coil
water supply temperature above freezing to avoid frost formation.
Equipment: Part 2
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