Abstract

The study investigates a hybrid radiant cooling system's potential to achieve thermal comfort. The hybrid radiant cooling (HRC) system combines the best features of a typical all-air and conventional chilled radiant cooling system. An HRC system presents the advantages to (a) reduce vapour condensation and to (b) adjust the cooling output by using an Airbox convector. The three systems perceive thermal comfort in the predicted mean vote (PMV) between –0.5 and +0.5 at 25 and 27°C. In the room condition at 31°C, the all-air system has a lower thermal comfort level because the elevated airspeed is less effective when the mean radiant temperature (MRT) is low. This study suggests a cooling strategy to maximize the thermal comfort level by effectively utilizing the HRC in extreme conditions without extra cooling sources. When the designed set point indoor temperature is 25°C, the Airbox convector of the HRC fan can be off. However, if the indoor air temperature increases above 25°C, an occupant can activate the Airbox convector; the actual thermal output of HRC is increased, and the elevated airspeed can reduce the predicted percentage dissatisfied (PPD) level. Even in an extreme indoor thermal condition at 31°C, the HRC minimizes the PPD level.

Highlights

  • The building construction sector is mainly responsible for greenhouse gas emissions, as buildings have consumed around 40% of total primary energy and a related 40% of total greenhouse gas emissions.[1,2,3] heating, ventilation and air conditioning (HVAC) systems result in the majority of energy consumption in buildings

  • In terms of presenting potential of the cooling systems, this study evaluated the performance of satisfying thermal comfort, predicted percentage dissatisfied (PPD) models and predicted mean vote (PMV), and of an hybrid radiant cooling system (HRC), in comparison with an all-air system and a conventional radiant cooling (CRC)

  • Kim et al.[6] investigated that HRC system can save a total of 9.3% of the cooling energy compared with the CRC system due to the higher coefficient of performance of the Chiller system as a lower exergy technology and higher cooling impact ratio

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Summary

Introduction

The building construction sector is mainly responsible for greenhouse gas emissions, as buildings have consumed around 40% of total primary energy and a related 40% of total greenhouse gas emissions.[1,2,3] heating, ventilation and air conditioning (HVAC) systems result in the majority of energy consumption in buildings. In the HRC system, a conventional radiant cooling panel and the compact Airbox convector are connected in series hydronically This novel system can minimize the disadvantageous characteristics of the allair and conventional radiant cooling (CRC) system and has several major benefits, including (1) reduction of vapour condensation risks, (2) enhancement of mixed convection effects by the Airbox fans, (3) minimization of the time delay to activate the system for thermal comfort, and (4) reduction of the indoor air pollutant concentrations by using an air filter.[6,15] Compared with a CRC system, the HRC system can save approximately 6–9% of the annual cooling energy consumption.[6] This is because the HRC system has a higher coefficient of performance (COP) of the cooling system and a higher cooling impact ratio compared to that of the CRC system, and it offsets the rise in operative temperature by raising the indoor airflow.[6,16]

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