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This paper first presents a temperature-transforming model to simplify the analysis and calculation of heat transfer in moist air. In this model, an apparent specific heat is defined as a function of temperature, humidity ratio, enthalpy of saturated water vapor, and the specific heats of dry air and water vapor. A correction factor is then proposed to rationalize the impact of moisture on dry air specific heat. Applying this model to analyze a typical air conditioning process demonstrates that an accurate enthalpy prediction along with a clear physical essence has been achieved. Secondly, an enthalpy-based expression of heat exchanger effectiveness is proposed to address the effects of thermal property on heat transfer analysis. A temperature-based effectiveness is then developed as a logic extension of the effectiveness discussion and the apparent specific heat method.