Nat Vorayos

Heat transfer prediction for a direct contact ice thermal energy storage

This research work studies the heat transfer characteristics of a direct contact evaporator. A cold two phase refrigerant (R12 or R22) is injected into water kept in a storage tank to exchange heat with the water directly. The water temperature is reduced to the freezing point, and ice could be formed. The lump model is used to predict the water temperature, and it is found that this model can predict the water temperature quite well. A correlation that relates the dimensionless parameters, such as Stanton number, Stephan number, Prandtl number and pressure ratio, is also developed.

Effect of the Electrode Arrangements in a Tube Bank on the Characteristic of Electrohydrodynamic Heat Transfer Enhancement: Low Reynolds Number

Enhancement in heat transfer using the electrohydrodynamic (EHD) technique is numerically examined in laminar forced convection across a tube bank with six different wire electrode arrangements. The electric field is generated by the wire electrodes charged with high DC voltages ranging from 7.5 to 17.5 kV. The Reynolds number corresponding to the flow considered is between 100 and 1,500. The numerical modeling of the laminar forced convection includes the interactions among the electric field, the flow field, and the temperature field. It is found that the heat transfer is significantly enhanced by the EHD at a low Reynolds number, and the short distance between the wire electrodes and the tube surface from which different electrode arrangements are reported for aligned and staggered tube configurations. The value Nu/Nu 0 of an aligned configuration increases from row to row and appears to be similar with that of a staggered configuration.