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RESEARCH PAPERS

# Initial Analysis of PCM Integrated Solar Collectors

[+] Author and Article Information
L. H. Alva S., N. Dukhan

Department of Mechanical Engineering, University of Puerto Rico-Mayagüez, Mayagüez, Puerto Rico 00681-9045

J. E. González1

Department of Mechanical Engineering, Santa Clara University, CA 95053igonzalezcruz@scu.edu

1

Corresponding author. Present address: Department of Mechanical Engineering, Santa Clara University, 500 El Camino Real, Santa Clara, CA, 95051.

J. Sol. Energy Eng 128(2), 173-177 (Dec 06, 2005) (5 pages) doi:10.1115/1.2188532 History: Received November 04, 2003; Revised December 06, 2005

## Abstract

This paper investigates the technical feasibility of innovative solar collectors. The proposed collectors have a phase change material (PCM) integrated into them as the storage mechanism. The PCM-integrated solar collector eliminates the need of conventional storage tanks, thus reducing cost and space. The present work uses a paraffin-graphite composite as the PCM to increase the conductivity of the PCM matrix. The paraffin’s melting point is around $89°C$, which is appropriate for use in single-effect absorption systems. The mathematical model that describes the thermal process in the PCM is presented and differs from the analysis of conventional flat plate solar collectors making use of the lumped capacitance method which neglects spatial variations. The proposed model is calibrated favorably with a more detailed mathematical model that uses finite differences and considers temporal and spatial variations. Results for the collectors’ thermal performance are presented along with the effects of the composition of the PCM. The results for the PCM integrated collector proposed here are very encouraging. Therefore, there is an indication that conventional storage tanks may be replaced for the PCM integrated in the solar collector.

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## Figures

Figure 1

Schematic of the PCM solar collector

Figure 2

PCM element configuration

Figure 3

Maximum paraffin weight (in percentage) and reduced storage thermal capacity versus density of the graphite matrix (loaded total porosity) (6)

Figure 4

Schematic representation of the PCM material for the simultaneous stage

Figure 5

Node arrangement used in the enthalpy method

Figure 6

Composite conductivity versus paraffin weight percentage

Figure 7

Comparison of the warming process of the PCM element for results given by the lumped capacitance method and the enthalpy method using five nodes

Figure 8

Comparison of the fraction of volume melted results given by the lumped capacitance method and the enthalpy method

Figure 9

Minimum composite area versus maximum mass flow rate for different inlet temperatures

Figure 10

Width and length of the composite material as function of mass flow rate (for constant inlet temperature of 80°C)

Figure 11

Collector area and collector efficiency versus width of the PCM material (for a mass flow rate equal to 0.00142kg∕s)

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