Experimental study of hydraulic and thermal behavior of an ice slurry in a shell and tube heat exchanger

Abstract

Experiments were conducted in a shell and tube heat exchanger with an ethylene glycol ice slurry flowing in the tubes and hot water in the shell. Pressure loss in the tubes, inlet and outlet density for the ice slurry, in addition to inlet temperature, outlet temperature and mass flowrate for both fluids were measured. A transient study with a slurry flowrate of 10 kg/min and water flowrate of 5 kg/min revealed that, when the ice concentration increases from 0 to 0.25 kg/kg, the heat transfer coefficient increases by 33% and the effectiveness increases by 18%. However, the pressure loss also increases by a factor of 2.3. The rate of increase of the heat transfer coefficient with mass flowrate is greater for a single phase fluid than for the ice slurry. The ice concentration has a greater impact on the heat transfer coefficient when the flowrate of the ice slurry is low. Overall heat transfer coefficients evaluated using two methods and twenty-one different correlations for the ice slurry were compared to values obtained from an energy balance. The most accurate results for turbulent flow were obtained using the Bell-Delaware method and the Colburn or Gnielinski correlations. For laminar flow the combination of Kern’s method with the correlation by Shah gave the best predictions of the overall heat transfer coefficient. The rate of increase of the pressure loss with ice concentration is small for concentrations between 0 and 0.15 kg/kg but increases for higher ice concentrations. Pressure losses calculated with several ice slurry correlations were compared to measured values. The more accurate correlations were those of Filonenko, Drew–Koo–McAdams and Blasius. The measured values indicate that at the outlet of the heat exchanger the solid and liquid phases are not in thermodynamic equilibrium; in fact ice exists for liquid temperatures higher than the melting temperature.