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Ventilation and air distribution methods are important for indoor thermal environments and air quality. Effective distribution of airflow for indoor built environments with the aim of simultaneously offsetting thermal and ventilation loads in an energy efficient manner has been the research focus in the past several decades. Based on airflow characteristics, ventilation methods can be categorized as fully mixed or non-uniform. Non-uniform methods can be further divided into piston, stratified and task zone ventilation. In this paper, the theory, performance, practical applications, limitations and solutions pertaining to ventilation and air distribution methods are critically reviewed. Since many ventilation methods are buoyancy driving that confines their use for heating mode, some methods suitable for heating are discussed. Furthermore, measuring and evaluating methods for ventilation and air distribution are also discussed to give a comprehensive framework of the review.

Abstract

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Unlike the case of air systems where the cooling load is purely convective, the cooling load for radiant systems consists of both convective and radiant components. The main objectives of this energy simulation study were to investigate whether the same design cooling load calculation methods can be used for radiant and air systems by studying the magnitude of the cooling load differences between radiant and air systems over a range of configurations and to suggest potential improvements in current design guidelines. Simulation results show that 1) zone level 24-hour total cooling energy of radiant systems can be 5-15% higher than air systems due to differences in conduction load through the building envelope; 2) peak cooling load at the radiant system hydronic level can be 7-31% higher than air system for zones without solar load. The differences can increase up to 93% at the hydronic level for floor system in zones with solar load; 3) the cooling load differences between the two systems originate from: a) radiant cooling surface(s) directly remove part of the radiant heat gain and reduce heat accumulation in the building mass; b) only part of the convective heat gain becomes instantaneous cooling load. This indicates that simplified methods such as Radiant Time Series Method is not appropriate for cooling load calculation in radiant system design. Radiant systems should be modeled using a dynamic simulation tool that is capable of capturing radiant heat transfer for cooling load calculation.