30 May 2005

PERFORMANCE OF COMPACT BRAZED PLATE HEAT EXCHANGER OPERATING AS CONDENSER IN DOMESTIC HEAT PUMP SYSTEM— AN EXPERIMENTAL INVESTIGATION


Brazed plate heat exchangers have become the preferred choice as heat exchangers in domestic heat
pumps by Swedish manufacturers, both as evaporators and condensers. The reason is the high heat
transfer rates at small temperature differences obtainable with this type of heat exchanger. At the Royal
Institute of Technology, a large number of measurements have been conducted on one specific condenser
under varying conditions. This paper reports area averaged condensation heat transfer coefficients under
operating conditions encountered in ground source heat pump applications. Two distinct regimes of heat
transfer mechanism are observed. For low overall heat transfer rates (many plates), the classical theory of
Nusselt yields reasonable values. For high heat transfer rates (few plates), the resulting condensation heat
transfer coefficient is significant higher than predicted by the Nusselt theory and the all-liquid convective
heat transfer coefficient yields reasonable agreement.