Estimation of River Water Temperature from Air Temperature: Using Least Square Method

Abstract

The water temperature plays a major role in application of Water-Source Heat Pump (WSHP) system. The water temperature is directly related to the energy efficiency of heat pump unit and economy of WSHP system. As the air temperature is the most influential factor in the water temperature in all meteorological parameters, the effect of air temperature on the changing water temperature should be considered first when estimating the river water temperature. In this paper, we dedicate to study the changing rule of water temperature with the air temperature by analyzing over one year water temperature data. Particularly, the least square method is used for the regression analysis of 1st-order to 6th-order curve, and a fitting curve is educed, based on Cubic model of the air temperature and the average of the corresponding water temperature. The 88% of the difference values between average water temperatures and fitted water temperatures are in the range of −1.5–1.5 °C. Therefore, it can provide a simple method to determine the daily average water temperature through analyzing the relationship between the water average temperature and air temperature by using the method of Cubic fitting. The study in this paper can be used as a reference for the design and analysis of WSHP system.