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RESEARCH PAPERS

Temperature Moderation in a Real-Size Room by PCM-Based Units

[+] Author and Article Information
S. Mozhevelov

Heat Transfer Laboratory, Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel

G. Ziskind

Heat Transfer Laboratory, Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israelgziskind@bgu.ac.il

R. Letan

Heat Transfer Laboratory, Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israelruthlet@bgu.ac.il

J. Sol. Energy Eng 128(2), 178-188 (Sep 06, 2005) (11 pages) doi:10.1115/1.2188531 History: Received December 22, 2004; Revised September 06, 2005

The objective of this work is to study the feasibility of temperature moderation inside a room using a phase-change material (PCM) which is stored in storage units. A real-size room which is at temperature conditions typical in a desert region in summer is considered. The idea is to use a phase change material which could melt during the day hours, absorbing heat from the room, while at night it solidifies due to a low night temperature. The heat from the room air to a PCM unit is free or forced-convected. The numerical model includes the transient heat conduction inside the walls/ceiling, free/forced convection of air, and radiation inside the room. The processes inside the PCM are modeled by the effective heat capacity (EHC) method. The PCM is assumed to melt and solidify within a certain temperature range, which represents the true situation for most commercial-grade phase-change materials. The numerical calculations are performed for the transient temperature fields inside the three-dimensional room, including PCM in the units, walls/ceiling, and the interior of the room. The boundary conditions for the room are chosen according to the experimental data which were obtained in previous works. The basic conservation equations of continuity, momentum, and energy are solved numerically, using the FLUENT 6.1 software. The numerical simulations are performed for at least one full 24-hcycle. Effect of different parameters on the behavior of the system is discussed, including the mass of the PCM and radiation effects inside the room. The night cooling by free and forced convection is analyzed. It is shown that a complete 24-hcycle is feasible in a properly designed configuration with a suitable PCM.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Physical model: (a) overall view; (b) vertical cross sections

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Figure 2

Laboratory-scale studies: (a) configuration used by Goldenberg (21); (b) numerical versus experimental results (Mozhevelov (22))

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Figure 3

Temperature evolution in the reference case

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Figure 4

Temperature and melt fraction evolution for 90kg of PCM

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Figure 9

Temperature distribution in the room air, ceiling, and walls for the case of 60kg of PCM with forced convection at nighttime

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Figure 10

Temperature distribution in the room air near the PCM units, for the case of 60kg of PCM with forced convection at nighttime

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Figure 11

A typical cycle of PCM melting and solidification, in terms of the temperature distribution inside the PCM

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Figure 12

Temperature and melt fraction evolution for 60kg of PCM (forced convection). Low emissivity of the unit walls.

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Figure 5

Temperature and melt fraction evolution for 60kg of PCM (free convection)

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Figure 6

Temperature distribution in the room air, ceiling, and walls for the case of 60kg of PCM with free convection at night time

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Figure 7

Temperature distribution in the room air near the PCM units, for the case of 60kg of PCM with free convection at night time

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Figure 8

Temperature and melt fraction evolution for 60kg of PCM (forced convection)

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