Dear all, I am a bit stuck trying to find out how heat is transfered through an evaporator in a refrigerator. I was using Newton's law of cooling before I realised there are more complexities in the equation as the refrigerant is in a mixture of saturated liquid and saturated gas in the evaporator. Newton's Law of cooling (heat transfer from a solid surface to a fluid): QL=UL*AL*LMTD where QL= heat transfer UL= overal heat transfer coefficient AL= external surface area of the evaporator LMTD= log mean temp different over the evaporator tube. i.e. The average temperature difference between the solid surface and the fluid (air in this case) across the evaporator inlet and outlet. My Question Is Newton's Law of cooling applied to refrigerator evaporators and/or condensers with this equation, for a simplified calculation? Or would the results be so far from correct that calculations must always take into consideration the boiling and condensing of the refrigerant?