Field measurements and numerical analysis on operating modes of a radiant floor heating aided by a warm air system in a large single-zone church

Ying Zhang,Chenbo Zhao,Thomas Olofsson,Gireesh Nair,Bin Yang,Angui Li

doi:10.1016/j.enbuild.2021.111646

Ying Zhang, Chenbo Zhao + Show 4 more

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https://doi.org/10.1016/j.enbuild.2021.111646

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Abstract

Space heating can constitute 60–80% of the total energy use of buildings in cold climates. Efficient heating techniques in buildings still rely on operating strategies. In this paper, a church with radiant floor heating in a cold climate is taken as a case of a large single-zone building to analyze the energy use for heating. Field measurements and numerical analysis are both used in the study. Different operating modes of heating, including intermittent heating and constant set-point heating, are compared for energy saving, reliability on indoor climate, and thermal comfort. The intermittent heating by an all-air system with supplied air temperature control results in the highest energy use. The constant set-point air temperature radiant floor heating aided by a warm air system (return air temperature control) is least affected by outdoor temperature with the best reliability and met the thermal comfort requirements throughout the heating season. The main novelty is that an operating mode of cyclic set-point air temperature is proposed. It is found that the small thermal inertia of heating systems should be preferred when the operating mode of cyclic set-point temperature is used to reduce the warm-up period. The results suggest how to operate and reduce the energy use of radiant floor heating systems in a large single-zone building.

Highlights

Buildings worldwide account for approximately 30% and 40% of the total final energy and primary energy use, respectively [1]
The main reason for the minor deviation between simulation and measurement results may be due to the control method of Radiant floor heating (RFH)
Compared with the operating mode of RFH with exhaust fans, the energy use of the allair system intermittent heating with supplied air temperature control increases by 11.7%, while the energy use of other operating modes (Case 5, 7 – 10) is reduced by 2.1% to 3.7% (Fig. 10)

Summary

Introduction

Buildings worldwide account for approximately 30% and 40% of the total final energy and primary energy use, respectively [1]. Space heating constitutes the majority of energy use in residential and non-residential buildings. Thermal comfort and energy-saving have always been a concern throughout the history of church heating technology development. Iron ovens were used for space heating and to raise the thermal comfort for sermons [2]. With the emergence of lowpressure steam technology and the implementation of fire protection regulations, iron stoves were gradually replaced. In the 1920s or 1930s, when the medieval or early modern churches were restored in Sweden, central heating was installed for the first time in the country [3]. The churches were heated intermittently for energy saving, often unheated for five or six days a week.

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