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In large space buildings such as check-in halls and departure halls in airports, the envelope is dominated by glass façades, skylights, and metal ceilings. A radiant floor is an effective sensible heat removal terminal due to its direct longwave radiant heat exchange with high-temperature wall surfaces and absorption of solar radiation. The emissivities of metal ceilings and many advanced materials (e.g., low-e coating) in large spaces range from 0.2 to 0.9, markedly different from that of traditional building materials (0.9–0.95), which affects the indoor longwave heat exchange. Moreover, the number of transient solar radiation incidents on the floor surface can vary tremendously, resulting in remarkable differences in cooling capacity of the radiant floor, e.g., from 30 to 40 W/m 2 to more than 100 W/m 2 . In this paper, a new simple calculation method for longwave radiant heat exchange that considers emissivity is proposed, and the location and duration of transient solar radiation through skylights and side windows in large spaces are depicted quantitatively. Based on this new method, a typical case study is presented, in which the cooling capacity of a radiant floor in the large spaces of an airport is calculated. The case study also showcases designs of radiant floors in large spaces with different material emissivity and transient solar radiation values. [ABSTRACT FROM AUTHOR]

In large space buildings such as airports, radiant floor systems are an attractive alternative to conventional all-air jet ventilation systems due to their advantages in thermal comfort and energy efficiency. This paper focuses on the operating performance of the radiant floor system in Terminal 3 of Xi’an Xianyang International Airport, the first airport terminal in China to adopt radiant floors for cooling. In summer, the typical cooling capacity of the radiant floor is 30–40 W/m 2 with a mean chilled water temperature of 18 °C; this range increases to 110–140 W/m 2 with solar radiation of 120–170 W/m 2 . The incremental effect of the solar radiation on the cooling capacity of radiant floor is analyzed with simple calculation methods. In winter, the radiant floor provides a heating capacity of 30–70 W/m 2 with a hot water temperature of 35–40 °C, which is sufficient to satisfy the heating requirement. Compared with the jet ventilation system adopted in Terminal 2 of the same airport, indoor thermal comfort is significantly improved with the radiant floor system in Terminal 3 in both cooling and heating modes. Moreover, the novel system’s indoor air temperature distribution throughout the whole space and its utilization of high-temperature chilled water and low-temperature hot water reveal its potential for energy conservation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dynamic behavior of typical radiant floors (RFs) is investigated quantitatively. [•] Time constant is used to reveal the thermal inertia of various RFs. [•] Cooling capacity of RFs is greatly improved with high-density solar radiation. [•] A simplified method for predicting dynamic cooling capacity of RFs is proposed. [•] Contracted calculation of peak load of chilled water in RF systems is provided. [ABSTRACT FROM AUTHOR]

Highlights: [•] Performance of a heat pump driven two-stage desiccant wheel system is analyzed. [•] Effects of heat pump system, desiccant wheel and working conditions are evaluated. [•] System COPt is 5.5 under Beijing summer condition with supplied air humidity of 10g/kg. [•] Cold–heat matching between heat pump and desiccant is the key to improve performance. [•] New system using an indirect cooler has better performance with COPt of 15% higher. [ABSTRACT FROM AUTHOR]

Highlights: [•] A simple method of predicting performance of radiant floor cooling is provided. [•] Cooling capacity of radiant floor is greatly improved with high-intensity solar radiation. [•] Radiant floor is suitable in large space building with high T envelope and solar radiation. [•] The effect of shelter of indoor furniture on the performance of radiant floor is analyzed. [•] Radiant floor systems show higher energy efficiency than conventional systems. [Copyright &y& Elsevier]

Abstract: Radiant floor is a low temperature heating and high temperature cooling system. Three parameters, cooling/heating capacity of radiant floor, uniformity of surface temperature distribution, and the lowest temperature in surface, are concerned most by designers and users of radiant floor. A simplified calculation of these parameters is presented in this paper. The error between experiment results in literature and calculation of cooling capacity and mean surface temperature is within 8% and 0.5°C respectively. A simulation model is established to verify simplified calculation on surface temperature distribution. The absolute error between simulation value and calculation is within 0.2°C. From the perspective of heat resistance, the most important limitation of cooling/heating capacity of radiant floor is heat transfer between floor surface and indoor environment. The thickness and heat conductivity of each layer has important influence on performance of radiant floor. The influence of water pipes should not be ignored. [Copyright &y& Elsevier]

Abstract: The temperature and humidity independent control (THIC) system, which controls indoor temperature and moisture separately, may be an attractive alternative to existing conventional HVAC systems for its prominent improvement on the overall system performance and utilization of low grade energy resources. In order to verify the effectiveness of THIC system, a pilot project has been implemented in an office building in Shenzhen, China. In the system, liquid desiccant fresh air handling units driven by heat pumps are utilized to remove the entire latent load of outdoor air supplied for the whole building, and chilled water at the temperature of 17.5°C from chiller is pumped and distributed into dry fan coil units and radiant panels to control indoor temperature. This paper presents the results of field test of the system, which shows that the system can provide a comfortable indoor environment even in very hot and humid weather. The COP of the entire THIC system can reach 4.0. According to the energy usage data recorded from the year 2009, the energy consumption of the THIC system in the tested office building was 32.2kWh/(m2 yr), which demonstrates magnificent energy-saving potential compared with the conventional air-conditioning system (around 49kWh/(m2 yr)). [Copyright &y& Elsevier]

• Flow distribution in an evaporator with 52 circuits was studied experimentally. • Face split design with enlarging header size reduced header ΔP and maldistribution. • Choked flow design of extra capillary tubes avoided liquid sucked into compressor. • Improved system presented even refrigerant distribution with various mass flow rate. • Cooling capacity and COP of the improved system increased by 10.5% and 13.4%. In this paper, the design concept of the face split evaporator with a retrofitted suction header and choked flow in the capillary tubes was adopted to improve a direct expansion air-conditioning system with a designed air flow rate of 20,000 m3/h. The novel design of the direct expansion air-conditioning system was experimentally tested and validated. Face split evaporator reduced the refrigerant pressure drop in the suction header and the choked flow design limited the maximum flow rate across each branch circuit, which both contributed to the uniform refrigerant flow distribution of the improved system. Consequently, the cooling capacity and COP of the improved system was 10.5% and 13.4% higher than the original system. With the refrigerant mass flow rate of the improved system varying from 1.33 kg/s to 2.05 kg/s, the measured cooling capacity ranged 240–350 kW and the ratio of the system COP to the ideal COP of the reversed Carnot cycle with the same evaporating and condensing temperatures maintained at 0.72–0.74. The experimental results demonstrated that the improved system performed a relatively uniform refrigerant flow distribution among the branch circuit of the evaporator regardless of the refrigerant mass flow rate. This study is beneficial to the optimization design of the multi-circuit evaporator for a direct expansion air-conditioning system with a large air flow rate in engineering applications. [ABSTRACT FROM AUTHOR]