关键词: 储热水箱, 间接式换热, 温度分层, 结构参数, 蓄热特性

Abstract:

The hot water tank in the solar heating system solves the problem of intermittent solar radiation and does not match the heat load. However, severe thermal stratification and mixing of hot and cold water in conventional thermal storage tanks hinder their ability to provide high-quality hot water, limiting the widespread deployment of solar heating systems. To enhance the thermal storage performance of these tanks, a mathematical model for the thermal storage process was established, and three-dimensional numerical simulations were employed to calculate the thermal storage characteristics, using the thickness of the thermocline layer and thermal storage capacity as performance indicators. The thermal storage characteristics of tanks with different configurations were analyzed using parameters such as the Nusselt number and the exergy. The research findings indicate that the original tank design with a bottom-mounted heat exchanger and no vertical pipe experienced the most severe water mixing, while a top-mounted heat exchanger yielded the best stratification effect but had a lower thermal storage capacity. Integrating a bottom-mounted heat exchanger with a vertical pipe significantly improved the stratification and thermal storage capacity of the tank. With this configuration, the tank’s thermal storage capacity increased by 18.87% within 3600 s, and the exergy increased by 1322.14%. The pump flow rate, vertical pipe height, and pipe diameter all influenced the tank’s thermal storage capacity and stratification effect. Optimal overall performance was achieved with a pump flow rate of 0.25 kg/s and a vertical pipe height and diameter of 1300 mm and 100 mm, respectively.

Key words: hot water storage tank, indirect heat exchange, temperature stratification, structural parameters, heat storage characteristic