Application of radiant cooling as a passive cooling option in hot humid climate

In hot and humid region, air-conditioning is increasingly used to attain thermal comfort. Air-conditioning is highly energy intensive and it is desirable to develop alternative low-energy means to achieve comfort. In a previous experimental investigation using a room equipped with radiant cooling panel, it was found that cooling water kept to 25 °C could be used to attain thermal comfort under some situations, while water at such temperature would not cause condensation of moisture from air on the panel. This paper reports results of a series of whole-year simulations using TRNSYS computer code on applications of radiant cooling to a room model that represents the actual experimental room. Admitting the inability of radiant cooling to accept latent load, chilled water at 10 °C was supplied to cooling coil to precool ventilation air while water cooled by cooling tower was used for radiant cooling in daytime application. For night-time, cooling water from cooling tower supplied for radiant cooling was found to be sufficient to achieve thermal comfort. Such applications are considered to be more amenable to residential houses.     

Numerical simulation of radiant floor cooling system: The effects of thermal resistance of pipe and water velocity on the performance

Using the existing floor heating system, the radiant floor cooling system can be used as an alternative to the conventional all-air cooling systems. In this paper, a numerical model for the radiant floor cooling system is built using finite volume method. The objective of this study is to research the effects of the thermal resistance of pipe and water velocity on the performance of the radiant floor cooling system. In order to provide better heat transfer simulation in the pipe, composite grids are used in the model. The numerical floor surface temperature and the heat flux are in agreement with the measured results. The results illustrate that the pipe has effect on the performance of the radiant floor cooling system when the thermal conductivity of the pipe is low. However, the effect of the water velocity on the performance of the cooling system is not great. The model is helpful to calculate and design such kind of radiant floor cooling systems.     

Practical cooling capacity estimation model for a suspended metal ceiling radiant cooling panel

The main thrust of this research was to develop a simplified cooling capacity estimation model for a suspended (free-hanging type) metal ceiling radiant cooling panel. By statistically analyzing panel performance data generated by a validated analytical panel model, the impact of various design parameters and their combinations on the panel cooling capacity was estimated. And then a linear regression equation was derived as a function of major design parameters and interactions which have significant effects on the panel capacity. In this analysis, eight single parameters and 13 two-factor interactions showed significant impact on the panel cooling capacity. Consequently, a simplified regression model for a free hanging panel was derived as a function of those selected parameters. The proposed model could estimate the panel cooling capacity not only for the natural convection but also for the mixed convection condition present in a mechanically ventilated space.     

Application of the control methods for radiant floor cooling system in residential buildings

In applying radiant floor cooling, its control system must prevent the floor surface condensation in hot and humid weather conditions. With no additional dehumidification system, only the radiant floor cooling system prevents floor condensation. In this case, the effects of the control of the cooling system on the indoor conditions can be changed because of the thermal inertia of the systems. Also different types of control system can be composed according to the control methods, which can affect the construction cost in the design stage. Therefore, the control methods for the radiant cooling system with respect to floor surface condensation must be studied. Furthermore, because Korean people's lifestyle involves sitting on the floor, it is necessary to evaluate if a floor cooling system will influence the thermal comfort of the occupants. This study intends to clarify the control methods of the radiant floor cooling system and to analyze the control performance and applicability of each control method with regard to the floor surface condensation and comfort by computer simulations and experiments on the control methods of the radiant floor cooling system. The results of computer simulations and experiments show that water temperature control is better than water flow control with respect to temperature fluctuations in controlling room air temperature. To prevent floor surface condensation, the supply water temperature could be manipulated according to the dew point temperature in the most humid room, and in individual rooms, the water flow rate (on/off control) can be controlled. Also, the results of radiant cooling experiments show that the floor surface temperature remained above 21 °C, the temperature difference among surfaces remained below 6 °C, and the vertical air temperature difference remained below 1.9 °C, conforming well to comfort standards.     

空调冷却水系统设计

论述了空调冷却水系统设计的基础参数，简述了空调冷却水系统设计的类型及其特点，提出了冷却塔设置应注意的几个问题及水质处理方法。     

地板辐射供冷系统的热性能研究

实验比较了双位开关控制、变流量控制和室外温度补偿+室温反馈控制方式下地板辐射供冷系统室内温度稳定性、地板表面温度稳定性以及结露发生频率.研究结果表明,室外温度补偿控制方式的最低供水温度为15℃,室外温度补偿率为0.25;在运行初期,双位开关控制室温稳定性优于其他控制方式,随着系统运行时间延长,室外温度补偿+室温反馈控制...     

Thermal comfort assessment and application of radiant cooling: A case study

A field assessment of thermal comfort was conducted at Mehran University of Engineering and Technology, situated in the subtropical region of Pakistan. The results show that people of the area were feeling thermally comfortable at effective temperature of 29.85 °C (operative temperature 29.3 °C). A comparison of this neutral effective temperature was made with the neutral effective temperature determined from adaptive models. It is found that the neutral effective temperature determined during this study closely match that of the adaptive model based on either indoor temperature or both indoor and outdoor temperatures. The results of thermal acceptability assessment show that more than 80% of occupants were satisfied at an effective temperature of 32.5 °C, which is 6.5 °C above the upper boundary of ASHRAE thermal comfort zone. Naturally ventilated classrooms and air-conditioned offices of the University were simulated using TRNSYS system simulation program for two cases, once when conventional air-conditioning is used for providing thermal comfort, and when comfort is achieved through radiant cooling. In the simulation, cooling tower was used to regenerate cooling water for the radiant cooling system. Energy consumption was estimated from simulation of both cases. The results show that it is possible to achieve thermal comfort for most of the time of the year through the use of radiant cooling without a risk of condensation of moisture from air on the radiant cooling surfaces. A comparison of the energy consumption estimates show that savings of 80% is possible in case thermal comfort is achieved through radiant cooling instead of conventional air-conditioning.     

Optimal design and operation of a thermal storage system for a chilled water plant serving pharmaceutical buildings

A group of buildings in the pharmaceutical industry located in Southern Germany is experiencing a trend of growing cooling loads to be met by the chilled water plant composed of 10 chillers of greatly varying cost effectiveness. With a capacity shortfall inevitable, the question arises whether to install an additional chiller or improve the utilization of the existing chillers, in particular those with low operating costs per unit cooling, through the addition of a chilled water thermal energy storage (TES) system. To provide decision support in this matter, an optimization environment was developed and validated that adopts mixed integer programming as the approach to optimizing the chiller dispatch for any load condition, while an overarching dynamic programming based optimization approach optimizes the charge/discharge strategy of the TES system. In this fashion, the chilled water plant optimization is decoupled but embedded in the TES control optimization. The approach was selected to allow for arbitrary constraints and optimization horizons, while ensuring a global optimum to the problem.     

Energy performance optimization of radiant slab cooling using building simulation and field measurements

Few field studies of energy performance of radiant cooling systems have been undertaken. A recently constructed 17,500 m² building with a multi-floor radiant slab cooling system in the tower was investigated through simulation calibrated with measured building energy use and meteorological data. For the very cold, dry region where the building was located, it was found that a typical floor of the tower would have had 30% lower annual energy use with a conventional variable air volume system than with the as-built radiant cooling-variable air volume combination. This was due to (1) simultaneous heating and cooling by the existing radiant cooling and air systems, (2) the large amount of free cooling possible in this climate, and (3) suboptimal control settings. If these issues were remedied and combined with improved envelope and a dedicated outdoor air system with exhaust air heat recovery, a typical floor could achieve annual energy use 80% lower than a typical floor of the existing building HVAC system. This shows that radiant thermal control can make a significant contribution to energy-efficiency, but only if the building design and operating practices complement the strengths of the radiant system.     

水冷却和汽化冷却以及空气冷却探析

介绍了水冷却、汽化冷却和空气冷却的过程，指出在实际应用中，可以采用汽化冷却同水冷却配合使用，空气冷却同水冷却配合使用，可取得良好的节水效果和经济效益。     

A field study of occupant thermal comfort and thermal environments with radiant slab cooling

This paper presents the findings of a field study of occupant thermal comfort and thermal environments with a radiant slab cooling system. The study combined field measurements and questionnaires based on the ASHRAE RP-921 project protocol. A total of 116 sets of data from 82 participants were collected in summer and winter. The results reveal that occupant whole-body thermal sensations with radiant cooling were consistent with the PMV model. The main advantage of radiant cooling for thermal comfort was found to be reduced local thermal discomfort with reduced vertical air temperature difference as well as reduced draft rate. The survey results revealed that 14–22% of participants in the study reported local cold discomfort in the arm–hand and the leg–foot regions. The results indicated that there may be lower limits on air speeds acceptable to occupants. Statistical analysis indicated that occupant thermal votes were free of significant correlation with personal, contextual and psychological factors. Suggestions to improve the questionnaire and the field survey process are offered.     

火力发电厂空调冷却水系统分析

通过对8个火力发电厂进行调研，收集了有关集控室空调冷却水的设计方案、水质资料及运行情况，分析结果表明，火力发电厂空调冷却水系统均满足生产及工艺要求。     

空调系统冷却水温度分析

在常用冷却塔计算方法的基础上,建立了适合空调用冷却塔出水温度的计算方法,并编写计算程序对不同状态下的空调用冷却水温度进行了计算,计算结果可以作为空调机组效率分析的基础。     

冷轧钢厂冷水系统设矿施工及运行管理

本文简要介绍某轧钢厂工艺用冷水、空调用冷水系统的设计。在理论分析及常规调试的基础上,结合现场实际情况对冷水系统进行全面分析。针对施工及运行管理中发现的问题,寻求解决措施。     

Experimental evaluation of heat transfer coefficients between radiant ceiling and room

The heat transfer coefficients between radiant surfaces and room are influenced by several parameters: surfaces temperature distributions, internal gains, air movements.The aim of this paper is to evaluate the heat transfer coefficients between radiant ceiling and room in typical conditions of occupancy of an office or residential building. Internal gains were therefore simulated using heated cylinders and heat losses using cooled surfaces. Evaluations were developed by means of experimental tests in an environmental chamber.Heat transfer coefficient may be expressed separately for radiation and convection or as one total parameter, but this choice may lead to different considerations about thermal performance of the system. In order to perform correct evaluations, it is therefore extremely important to use the proper reference temperature.The obtained values confirm tendencies found in the literature, indicating limitations and possibilities of radiant ceiling systems improvement.     

冷却顶板空调系统中热环境分析

采用CFD软件,探讨了某通透大型玻璃幕墙建筑顶板冷辐射空调系统中的空调方案对室内热环境的影响,并进行了热舒适评价,研究表明：在不能安装辐射换热管系统的部分空间内,可以采用安装地板辐射管,并采取适当的通风方式带走室内余热以达到设计要求。     

敞开式循环冷却水系统的水质处理

介绍了循环冷却水系统水质处理的目的，并就循环冷却水水垢的形成及腐蚀的机理和影响因素作了分析，提出了水垢及腐蚀的控制方法和措施。     

The response of a complex Data Centre chilled water system to an unplanned site-wide power failure and the influence on the Data halls

The paper describes the modelling and analysis of a 10 MW chilled water distribution system that is used for the cooling of parallel Data halls. During an unplanned site power failure, the Chillers may go offline for some minutes, affecting the temperature and delivery of chilled water to the Data hall cooling units. This may cause the air temperature within the Data halls to rise. The ultimate test of robustness is to ensure that the IT equipment is adequately cooled during this time. This work outlines the key findings from the thermal response of the cooling system to a site power failure. The entire chilled water network that comprised the primary and secondary plant was modelled, including components such as pumps, valves and Chillers. A transient analysis was conducted to predict the rise in water temperature at different locations in the system. Computational fluid dynamics was then adopted to predict the air temperature reaching the IT equipment, therefore confirming the capability of the design to steer clear of effects such as thermal runaway. The findings demonstrate that confidence in the omission of expensive buffer vessels and UPS backed plant could not have been achieved without the advanced transient analysis conducted here.     

循环水和冷水系统的一种节能运行方式

对常规的循环水、冷水系统运行方式进行了比较分析,提出了在过渡季节冷却塔参与到冷水系统的运行方式可以降低运行费用的方法,通过实例的运行情况研究总结得出结论,该运行方式节能效果明显。     

国际大厦常规冷却与海水冷却方案比较

结合一个濒海工程实例，具体地分析了常规冷却与海水冷却方案在设备投资，运行费用和占用面积等方面的差异，得出了就该工程而言，海水冷却方案明显优于常规冷地方案的结论，同时指出有前者的实施过程中必须注意的几个问题。