Evaluating convection-radiation systems: The effect of supply water temperatures and operation strategies in different System designs

Abstract

This study investigates the operational characteristics of a convective-radiative cooling system in hot summer and cold winter regions. It focuses on analyzing how the system's structural design and operational strategy affect energy consumption and indoor comfort. Laboratory tests were conducted on two types of dry-wet combined convective-radiative cooling systems (System 1 and System 2). A comprehensive analysis was performed on the effects of different water supply temperatures and operation modes on indoor environmental conditions, energy consumption, and comfort. Findings highlight the significance of terminal structures in improving the efficiency of these systems. Results show that System 1 typically maintains room temperatures about 1 °C higher than System 2, which benefits from enhanced stability due to its concrete filling layer. The study also notes a possible hot water mixing issue in System 1's buffer tank. Transmission and distribution system energy for these systems ranges from 12.5 % to 23.3 %, increasing with water temperature. Both systems can reduce energy consumption by 45.9 %–49.2 % in different modes, and increasing the water supply temperature to the main unit can further decrease energy use by 6.7 %–29.5 %. Continuous operation ensures stable Predicted Mean Vote (PMV) levels, while intermittent operation allows the PMV to quickly reach the recommended range. Both systems demonstrate low sensitivity to changes in supply water temperature in terms of operational effectiveness. This study recommends using intermittent operation with high-temperature water cooling, starting system 1–2 h before use for an optimal balance between energy efficiency and comfort. This provides a comprehensive perspective for enhancing convective-radiative systems cooling and offers practical suggestions for their design and operational strategies.