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VERY LOW ENERGY CONSUMPTION HVAC SYSTEMS FOR NZEB BUILDINGS. THE POTENTIAL OF INDIRECT EVAPORATIVE COOLERS IN SOUTH EUROPEAN CLIMATES
F. Comino, F. Peci, M. Ruiz de Adana
Keywords: indirect evaporative cooling, energy efficiency, NZEB buildings 1. Introduction
Development of very low energy consumption HVAC (Heating, Ventilation and Air Conditioning) systems are required in the European frame of NZEB (Nearly Zero Energy Building). Evaporative cooling systems are an effective alternative to conventional technologies, due to their high efficiency and reduced primary energy consumption (Duan, 2012). There are two main types of evaporative coolers: the direct evaporative cooler (DEC), and the indirect evaporative cooler (IEC). DEC is based on direct contact between air and water, while IEC is based on heat and mass transfer between two streams of air, separated by a heat transfer surface with a dry side, where only air is cooling, and a wet side, where water is evaporated into air (Porumb, 2016). In addition, there are different types of IEC: conventional IEC, which supplies air between the dry bulb temperature, Tsb, and the wet bulb temperature, Twb; regenerative evaporative cooler (R-IEC), including single-stage counter-flow, and finally, Maisotenko-cycle (M-IEC), including multi-stage cross-flow. The last two supply air between the dry bulb temperature, Tsb, and the dew point temperature, Tdp. These types of evaporative cooler systems are shown in Table 1. This work focused on the study of R-IEC.
Table 1. Types of evaporative cooler systems (Porumb, 2016).
(a) DEC (b) IEC (c) R-IEC (e) M-IEC
Twb <T<Tsb Twb <T<Tsb Tdp <T<Tsb
The main objective of this study was to determine numerically the energy efficiency of a R- IEC air-cooling system for typical summer air conditions in Cordoba, Spain.
2. Materials and methods
The R-IEC study in this work is a self-contained device, mainly composed of a core heat and mass exchanger, a low energy consumption centrifugal fan, a water distributing system and an outer casing. The primary air of the device is cooled along the dry channels without moisture increase and, subsequently, discharged. Through the perforations located at the end of the channels, a portion of the primary air is diverted into the adjacent wet channels. Flowing in counter direction to the primary air in dry channels, the secondary air of wet channels is humidified,
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