Experimental study of ammonia flooded boiling on a triangular pitch plain tube bundle

Flooded ammonia shell and tube heat exchangers are widely used in refrigeration systems for various fluid cooling applications. Ammonia as a natural refrigerant with zero Ozone Depletion Potential (ODP) and zero Global Warming Potential (GWP) is getting unprecedented attention due to the current potential phase out of hydroflourocarbons (HFC's). This paper presents the results of an extensive experimental work on boiling of ammonia in a flooded triangular pitch plain tube bundle evaporator with saturation temperature range of −1.7 to −20 °C and heat flux range of 5-45 kW/m2. These ranges fall well within the practical operating conditions in the real world industrial refrigeration systems. Heat transfer coefficient showed classical behavior of increase with both saturation temperature and heat flux. A correlation for outside boiling in a tube bundle was developed and compared with existing general pool boiling correlations and with limited ammonia boiling data on single plain tubes and bundles. A pass to pass bundle performance was also investigated.