Open Access

ARTICLE

Impact of Window-to-Wall Ratio on Thermal Comfort and Energy Performance of Hybrid Cooling Systems

Dong Liu¹, Runze Zhang¹, Anjie Hu¹, Na Liu¹, Liu Tang^2,3,*, Xiaozhou Wu⁴, Jun Wang^2,5

1 School of Civil Engineering and Architecture, Southwest University of Science and Technology, Mianyang, 621010, China
2 Sichuan Province Engineering Technology Research Center of Healthy Human Settlement, Chengdu, 610065, China
3 Sichuan University Engineering Design & Research Institute Co., Ltd., Chengdu, 610065, China
4 School of Civil Engineering, Dalian University of Technology, Dalian, 116081, China
5 College of Architecture and Environment, Sichuan University, Chengdu, 610065, China

* Corresponding Author: Liu Tang. Email:

(This article belongs to the Special Issue: Fluid Mechanics & Thermodynamics in Renewable Energy and HVAC Systems)

Fluid Dynamics & Materials Processing 2025, 21(10), 2579-2612. https://doi.org/10.32604/fdmp.2025.070407

Received 15 July 2025; Accepted 28 September 2025; Issue published 30 October 2025

Abstract

This study compares two end-cooling systems, convective–radiant combined cooling (FR+FC) and fan coil convection (FC), through continuous experimental investigations, focusing on the impact of window-to-wall ratio (WWR) on indoor thermal comfort, temperature distribution, humidity, and energy consumption. Results show that increasing WWR amplifies indoor temperature fluctuations. While the overall predicted mean vote (PMV) remains within the Level-II comfort range (−1.0 to +1.0), the FC system exhibits pronounced local PMV gradients near west-facing windows, especially at 80% WWR, where transient PMV reaches 1.26 close to the window, 0.89 higher than at the room center. In contrast, the FR+FC system significantly reduces spatial PMV variations, maintaining local PMV within acceptable limits for most of the day. Energy analysis reveals that FC energy consumption rises with WWR, increasing by 7.11% from 40% to 80% WWR, whereas FR+FC energy use decreases by 29.26% over the same range, demonstrating its superior handling of radiant loads. Furthermore, the convective–radiant system exhibits a high average hourly cooling performance coefficient. These findings indicate that FR+FC systems provide better thermal comfort and energy efficiency in high-WWR spaces, making them particularly suitable for summer operation in window-intensive buildings.

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Keywords

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