Dehumidification-adjustable cooling of radiant cooling terminals based on a flat heat pipe

Wu, Yunyi; Sun, Hongli; Duan, Mengjie; Lin, Borong; Zhao, Hengxin

doi:10.1016/j.buildenv.2021.107716

Cited by 19 publications

(6 citation statements)

References 35 publications

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“…where Q c represents the effective heat dissipation of the FHP cooling radiator, W; Q is the total heat dissipation of the FHP cooling radiator, W; c is the heat capacity of water, J•kg −1 K −1 ; G is the flow rate of the circulation system, kg•h −1 ; A is the total area of the FHP cooling radiator, m −2 ; A c is the heat dissipation area of the FHP cooling radiator, m −2 ; ∆T is the temperature difference between the two thermal resistances, K. Wu et al [139] proposed a new radiant cooling terminal integrated with the HE and the FHP (shown in Figure 55). To decouple the condensation prevention and cooling capacity improvement, the running strategy in which the FHP was only used for removing the sensible heat load while the HE was used for removing the sensible and latent heat load simultaneously was proposed.…”

Section: Cooling Radiator Integrated With Hpmentioning

confidence: 99%

The Review of the Application of the Heat Pipe on Enhancing Performance of the Air-Conditioning System in Buildings

Yuan,

Liu,

Zhang

et al. 2023

Processes

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An air-conditioning system (ACS), which consumes large amounts of high-grade energy, is essential for maintaining the indoor thermal environment of modern buildings. However, an ACS consumes almost half of the total energy of the building. Therefore, it is necessary to reduce the energy consumption of the ACS to promote energy conservation and emission reduction in the building sector. In fact, there is an abundance of waste heat and low-grade energies with the potential to be utilized in ACS in nature, but many of them are not utilized efficiently or cannot be utilized at all due to the low efficiency of thermal energy conversion. Known as a passive thermal transfer device, the application of a heat pipe (HP) in the ACS has shown explosive growth in recent years. HPs have been demonstrated to be an effective method for reducing building cooling and heating demands and energy consumption in ACS with experimental and simulation methods. This paper summarizes the different HP types applied in the ACS and provides brief insight into the performance enhancement of the ACS integrated with HP. Four types of HPs, namely tubular HP (THP), loop HP (LHP), pulsating HP (PHP) and flat HP (FHP), are presented. Their working principles and scope of applications are reviewed. Then, HPs used in natural cooling system, split air conditioner (SAC), centralized ACS (CACS) and cooling terminal devices are comprehensively reviewed. Finally, the heat transfer characteristics and energy savings of the above systems are critically analyzed. The results show that the performance of the HP is greatly affected by its own structure, working fluid and external environmental conditions. The energy saving of ACS coupled with HP is 3–40.9%. The payback period of this system ranges from 1.9–10 years. It demonstrates that the HP plays a significant role in reducing ACS energy consumption and improving indoor thermal comfort.

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Section: Cooling Radiator Integrated With Hpmentioning

confidence: 99%

The Review of the Application of the Heat Pipe on Enhancing Performance of the Air-Conditioning System in Buildings

Yuan,

Liu,

Zhang

et al. 2023

Processes

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“…Compared with conventional air-conditioning systems, radiant cooling has been verified to have many advantages (Rhee and Kim, 2015), including energy conservation (Niu et al, 2002;Hassan and Abdelaziz, 2020;Li et al, 2020), thermal comfort (Tian and Love, 2008;Kim et al, 2018;Karacavus and Aydin, 2019), and indoor air quality (Jagjit et al, 2010;Saber et al, 2014). However, due to the restriction of dew point temperature on cooling source temperature (Wu et al, 2021), the cooling capacity was limited, which hindered the application of radiant cooling in hot and humid areas (Rhee et al, 2017;Ning, 2020).…”

Section: Introductionmentioning

confidence: 99%

Improving Cooling Capacity of Condensation-Free Radiant Cooling for Low-Emissivity Chilled Ceiling via Adaptive Double-Skin Infrared Membranes

Du¹,

Wu²,

Guo³

et al. 2022

Front. Therm. Eng.

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Radiant cooling has well been acknowledged as energy efficient and thermal comfortable technology compared to conventional convective cooling. However, the radiant cooling exists two serious problems (viz., insufficient cooling capacity and high condensation risk) especially in hot and humid climate zones. By adding double-skin infrared transparent membranes (DIMs) onto radiant cooling panel, the air-contact surface can be separated from the cooling source surface, which makes it possible to use a low-temperature cooling source while maintaining air-contact surface higher than dew point temperature. The DIMs are transparent to radiant heat transfer which yields great cooling capacity while chilled ceiling has high emissivity (e.g., above 0.9). However, for metal chilled ceilings having low emissivity, radiant heat from cooling load to chilled ceiling would be reduced through DIMs, which results in insufficient cooling capacity. In this paper, a type of adaptive double-skin infrared membranes (a-DIMs) consisting a high-emissivity membrane and a high transparent membrane is proposed to improve cooling capacity of conventional metal chilled ceilings. The high-emissivity membrane serves as radiant cooling surface instead of low-emissivity chilled ceiling so as to improve radiant heat flux, while the high transparent membrane permits great radiant heat from cooling load to chilled ceiling. A combined heat transfer analysis based on semi-transparent surface radiation and natural convection were carried out to predict cooling capacity of condensation-free radiant cooling. The results indicate that the cooling capacity could be up to 101.9W/㎡ by adding a-DIMs consisting of a high-emissivity membrane of 0.96 and a high transparent membrane of 0.87, which is improved by 2 times compared to conventional metal chilled ceiling with low emissivity of 0.2. Moreover, the cooling capacity by adding a-DIMs is further improved by 25% compared to that by using both infrared transparent DIMs presented in our previous work. The results also indicate that the cooling capacity could be improved by above 2 times compared to conventional low-emissivity metal chilled ceiling by using the radiant cooling with a-DIMs for various humidity. It will be of great guidance for high-performance radiant cooling design without condensation and improved cooling capacity for low-emissivity metal chilled ceiling.

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“…However, RC systems' cooling capacity in humid environments is limited due to the risk of condensation on the panel surfaces [20]. Several designs have been proposed to combine RC systems with dehumidification to expand their applicability [20][21][22][23][24]. These systems can broadly be categorised into two groups: dedicated outdoor air systems (DOAS), where the supply air entering the conditioned space is dehumidified, and systems that include a separate condensing unit inside the conditioned space.…”

Section: Introductionmentioning

confidence: 99%

“…DOAS systems are often large, complex and have comparatively high material and installation costs [21,23], which means their application in small-sized buildings is challenging. They also often require embedding components into building structures [25], limiting their application in retrofit projects.…”

Section: Introductionmentioning

confidence: 99%

“…Separate condensing unit designs include an open collector for the condensed water in the conditioned zone, which poses a health hazard [23]. Furthermore, the dehumidification unit can be positioned either horizontally (in the ceiling), which poses challenges for condensate collection, or vertically (on the wall), leading to suboptimal heat transfer and taking some valuable floor area in the conditioned space, which is inconvenient for the users [21]. For these reasons, other dehumidification methods that are better suitable for small-scale retrofit projects are needed.…”

Section: Introductionmentioning

confidence: 99%

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Performance Analysis of a Geothermal Radiant Cooling System Supported by Dehumidification

et al. 2022

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Space cooling demand is increasing globally due to climate change. Cooling has also been linked to all 17 sustainable development goals of the United Nations. Adequate cooling improves productivity and thermal comfort and can also prevent health risks. Meanwhile, policy initiatives such as the European Union’s Green Deal require participants to cut greenhouse gas emissions and reduce energy use. Therefore, novel cooling systems that are capable of efficiently producing high levels of thermal comfort are needed. Radiant cooling systems provide a design capable of fulfilling these goals, but their application in hot and humid climates is limited due to the risk of condensation. In this study, we compare the performances of radiant cooling systems with and without dehumidification. The studied systems are supplied by geothermal energy. The study is conducted using building energy models of a small office building belonging to a three-building school complex located in Sant Cugat near Barcelona in Spain. The studied location has a Mediterranean climate. The simulations are conducted using IDA Indoor Climate and Energy 4.8 simulation software. The results show that the radiant cooling system with dehumidification (RCD) produces considerably improved thermal comfort conditions, with maximum predicted mean vote (PMV) reached during the cooling season being 0.4 (neutral) and the maximum PMV reached by the radiant cooling system without dehumidification (RC) being 1.2 (slightly warm). However, the improved thermal comfort comes at the cost of reduced energy and exergy efficiency. The RCD system uses 2.2 times as much energy and 5.3 times as much exergy as the RC system. A sensitivity analysis is also conducted to assess the influence of selected input parameters on the simulation output. The results suggest that maximising dehumidification temperature and minimising ventilation flow rate can improve the energy and exergy efficiency of the RCD system while having a minor effect on thermal comfort.

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Dehumidification-adjustable cooling of radiant cooling terminals based on a flat heat pipe

Cited by 19 publications

References 35 publications

The Review of the Application of the Heat Pipe on Enhancing Performance of the Air-Conditioning System in Buildings

The Review of the Application of the Heat Pipe on Enhancing Performance of the Air-Conditioning System in Buildings

Improving Cooling Capacity of Condensation-Free Radiant Cooling for Low-Emissivity Chilled Ceiling via Adaptive Double-Skin Infrared Membranes

Performance Analysis of a Geothermal Radiant Cooling System Supported by Dehumidification

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