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The paper evaluates the feasibility of implementing nocturnal radiative cooling system for air comfort application. Mechanical air conditioners are conventional in creating thermal comfort but are energy-intensive and hence harmful to the ecological system. Therefore, passive cooling can be adopted as a viable alternative to conventional cooling system. Heat flow through the roof contributes to the total heat gain of a building. The contribution becomes more severe for single story houses covered by metal sheet roofing. An aluminum nocturnal radiator thickness of 0.44 mm and 0.55 mm, painted with an appropriate white paint, was established on the roof. The lightweight metallic radiator was used for cooling the ambient air below its initial temperature. Consequently, this environment-friendly and highly-efficient system can reduce the use of mechanical vapor compression systems. Roofs of buildings radiate heat day and night at a rate of up to 75 W/m2. Generally, most locations can provide net night sky radiation above 60 W/m2, while the nocturnal coolers have the potential of reducing space temperatures by 2 to 4 °C and can yield 14-48% savings in the energy demand of a building. [ABSTRACT FROM AUTHOR]

The increasing complexity of modern architectural geometries emphasizes the need for more accurate simplified calculations of comfort analysis in architectural design. In most applications, the designer roughly estimates several parameters involved in thermal comfort that are very difficult to compute, among which the components of Mean Radiant Temperature (MRT) are notable. The goal of this paper is to propose a fast reliable technique, named Numerous Vectors (NV), to calculate MRT even in the presence of complex geometries. Considering the area, orientation, and distance of different radiant geometries, the process suggests an innovative method to find geometric-related parameters such as view factors by projecting the surrounding surfaces on a unit sphere representing the human body. The NV method is much faster than conventional methods. Moreover, all the geometry-related components of MRT including the radiation of individual surfaces, solar radiation, and the atmospheric radiation are calculated in one single step. The results are proved to be in a good agreement with analytical data. [ABSTRACT FROM AUTHOR]

A new detailed transient model for PVT-water collectors is presented. The model uses a nodal approach based on the electrical–thermal analogy using RC networks to model the thermal response of the PVT collector. Unlike models found in the literature, the RC network is directly used to simulate the PVT collector in an electronic circuit simulator. Heat flow is modelled in one dimension only and average temperatures are used for the fluid and absorber plate in order to calculate the transient thermal output of the collector. A discussion on the correct calculation of the average temperatures for the collector and possible approximations is presented. The model was used to simulate a PVT collector coupled to a domestic hot water load, in order to study the daily performance of a PVT-water system and its transient behaviour. Results show that the proposed solution can achieve extremely good agreement with experimental data, and that the model could be used for performance analysis and product design. [ABSTRACT FROM AUTHOR]