Ice-maker heat pumps are a special kind of water. source heat pump in which the flowing water is allowed to freeze on the evaporator surfaces. The problems of freezing and melting present special mathematical complexity and, except for the most elementary onedimensional cases, require a numerical solution.
In the present work, a numerical model for ice formation from flowing water in a finned annular sector of an evaporator is developed. The model predicts ice profiles as a function of axial position and time, and energy transfer values as a function of time. The rnodel also allows flow direction reversals in the annular sector° Reversing the flow de-ices the evaporator surfaces by causing part of the ice to melt or detach from the wall. 7his de-icing enhances the energy transfer values. Therefore, the flow reversal method is suggested as art alternative for de-icing without the losses commonly associated with the conventional de-icing methods.
The results of the preliminary evaporator evaluation show a large energy transfer gain for the reversal case as compared to the energy transfer obtained without reversal. Most of the gain comes from an increased cooling of the liquid water (more sensible energy from the water is be#tg transferred to the refrigerant). The model predicts only a small arnount of ice detachment from the evaporator. The study includes a third alternative. This consists of interrupting the refrigerant flow for a few seconds after each reversal, with the purpose of obtaining additional ice detachment. Overall heat transfer results for this case closely follow those for reversal without refrigerant flow interruption.
Further study in this area is recommended for com.. pleting the evaluation of the evaporator. This includes a comparison with existing de-icing alternatives and an extensive parametric study of the system.
Citation: ASHRAE Transactions, vol. 95, pt. 2, Vancouver, BC 1989
Product Details
- Published:
- 1989
- Number of Pages:
- 9
- File Size:
- 1 file , 1000 KB
- Product Code(s):
- D-27172
