ZEMCH 2019 International Conference Proceedings April.2020 | Page 134
1. Introduction
From previous studies, it was clear that buildings account for 36% of worldwide energy
consumption, which in turn equates to 40% of annual greenhouse gas emissions [1]. Residential
buildings have been identied as one of the few sectors that have the potential to see large energy
savings through the utilization of renewable energy and green building concepts [2]. Integrating high
thermal performance PCMs in building is an effective technique to reduce energy consumption in
buildings [3]. PCMs can reduce the indoor temperature values providing thermal comfort of the space.
Therefore, increasing the energy efciency and improving the thermal comfort for occupants [4].
Utilizing this technology can achieve a reduction in energy consumption of buildings reaching up to
30%, depending on the application [5]. PCMs are organic and inorganic compounds. Both types have
different storage capacity and temperatures of phase change transitions. The most commonly used and
known PCMs are paraffin waxes and salt hydrates [6‐8]. Phase changes solid/liquid and solid/solid is
the attractive form to be applied as a thermal energy storage system in the building applications with
a milting temperature point ranges from 0 °C to 100 °C due to small volumatic change of 10% during
the phase transition [9].
Optimization PCM are known as an effective technology to store larger amounts of thermal energy
per unit mass than conventional thermal mass building materials such as concrete and stone [3]. They
add thermal stability to lightweight constructions without adding physical mass. Therefore, integrating
PCMs with building envelopes to improve indoor thermal comfort level [7] and save energy attracted
so many attentions from researchers all over the world. Similar to the PCMs optimized building
envelopes, PCM storage systems can also be put into air cooling, heating, and ventilation systems to
store thermal energy from the evaporator or condenser and thus improve indoor thermal level.
Therefore, PCM has been widely used in air‐conditioning, building materials, textiles, energy‐saving
equipment, health care, food preservation and warm supplies as one of the typical environmentally
friendly energy saving materials [10‐11]. PCMs used in building equipment could improve indoor
thermal comfort by regulating air temperature, and effectively increase the energy efficiency of air
cooling, heating, and ventilation systems. [12]
Based on PCM‐TES and free cooling system, PCM window‐based cooling unit was developed by
many researchers. At night, outdoor coolness was stored in the unit by natural ventilation and it was
actively released to indoor environment during daytime. The simulation results showed that the PCM
slabs with optimum thickness of 5 mm could freeze completely within 7 h from 21:00 to 4:00. On the
other hand, for improving summer comfort in domestic residence, a PCM stock was coupled with
summer ventilation system [13]
The previous results confirm that the temperature peaks in a local equipped with PCM insulation
could be reduced up to 5 °C (various studies achieved proclaim temperature reductions between 3 and
5 °C), and the electricity consumption linked to air‐cooling system could decrease by 30% [14].
The purpose of this paper is to design and evaluate novel PCM based air pre‐cooling system placed
in the AC duct system, the characteristics required for effective and predictable thermal energy storage
excludes many PCMs which used for higher temperature ranges recommending paraffin and salt
hydrates with preferable characteristics of higher thermal energy storage and suitable melting range.
2. Materials and Methods
The methodology of this paper is composed of integrating the PCM (paraffin wax) into the air
conditioning duct system and evaluate its pre‐cooling performance. The hot air will be supplied to the
test chamber with specified velocity while the PCM containers will be placed facing the hot air. The hot
air will bump the surfaces of the PCM containers allowing the heat to transmit to the PCMs. The PCM
will work as latent heat storage units cooling the surrounding air. The cooling effect is quantified by
the drop‐in air temperature at the outlet of the duct as compared to the inlet air temperature. The PCM
associated cooling effect is presented and numerically modeled. The numerical model is employed to
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ZEMCH 2019 International Conference l Seoul, Korea