Abstract
Energy storage is one of the most effective ways to increase energy savings and efficiency of heating and air conditioning systems. Phase change materials (PCMs) are increasingly used in latent heat thermal energy storage (LHTES) systems to increase their capacity. In such systems, costs are a very important factor of viability so the typical heat transfer elements like fin-and-tube heat exchangers are used to construct the LHTES. The problem of this approach is a possibility of corrosion of metals in contact with PCM that shortens the life cycle of LHTES. Therefore, the main objective of this work is an experimental study of the compatibility of metals typically used in fin-and-tube heat exchangers (copper and aluminum) with three commercially available organic PCMs (RT15, RT18HC, and RT22HC). Compatibility of PCMs with copper and aluminum was tested for a period of approximately two months, during which a total of 35 heating and cooling cycles were carried out, each with a complete phase transition of the tested materials. In the course of the tests it was assessed whether the PCM caused corrosion of the tested metals. The evaluation was based on the gravimetric method, calculation of corrosion rate, and visual observations and measurements of the features on the metal sample’s surface using optical microscope. It was determined that RT15, RT18 HC, and RT22 HC show low corrosion rates for aluminum and copper samples. The visual tests indicate that there was no change in the PCM solutions during the tests, only a sediment was observed for the samples with the combination of copper and aluminum. Microscopic examination of the surface of the samples did not show any significant surface changes, except for the aluminum samples, on the surface of which local microdefects were observed. It follows from the present results that copper and aluminum can be used to design the heat transfer surface in contact with the chosen PCMs.
Highlights
Energy consumption in the construction sector is 40% of the global value and is responsible for 36% of greenhouse gas emissions to the atmosphere [1]
The results presented in this paper highlight that it is important to conduct Phase change materials (PCMs) compatibility studies for samples with two metals in contact because they may show different effects than when each of the metals is tested separately
It was decided to determine the compatibility between commercially available organic PCMs and materials found in a typical fin-and-tube heat exchanger, which could be used as the structural material of the latent heat thermal energy stores (LHTES)
Summary
Energy consumption in the construction sector is 40% of the global value and is responsible for 36% of greenhouse gas emissions to the atmosphere [1]. The results of the study presented and discussed in this paper are part of research that is focused on a real industrial case where there was a mismatch between capacities of the heating system and the adsorption chiller operating in an office building’s AC system. In this situation, the mass flow rate of available hot water was too low to properly supply the adsorption chiller during peak load periods. A thermal energy storage system with a phase change material (PCM) was suggested to reduce peak cooling load demand
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