Heat pipe heat recovery for passive stack ventilation.

Four types of heat-pipe heat recovery systems were tested for application in passive stackventilation. The effects of fin shape, pipe arrangement and air velocity on the heat recoveryeffectiveness were investigated. The air velocity was found to have a significant effect on theeffectiveness of heat recovery; the effectiveness decreasing with increasing air velocity.The pressure loss coefficient for heat pipe units was also determined. It was found that at lowvelocities for natural ventilation the pressure loss coefficient decreased with increasing airvelocity but the total pressure loss increased with the velocity. It is recommended that innaturally-ventilated low-rise buildings, without the wind effect or solar energy, the design ductmean velocity should be less than 1 m/s in order for a heat recovery system to functionproperly. The use of a solar chimney and/or wind turbine could increase the range of airvelocity and so the amount of heat recovery.