The testing apparatus consisted of an isolated cylinder volume of 0.45 m length and 0.18 m inner diameter. Five lamps each with a wolfram filament, were installed inside this volume. Electrical power for each lamp was 1 kWt. It was possible to use any number of lamps due to special switch. Visual observation made it possible to study the distribution of liquid and solid phase during melting-freezing cycles. The empty volume with a gas and the same volume with solid PCM during freezing process had a darker color with respect to the capsule volume. The measurements of surface temperature were made with thermocouples placed circumferentially on the outer and the inner surface of the capsule. Before the experiment, every capsule was filled with liquid PCM in a special device and was sealed also in special device by welding in argon. The properties of the PCM and the capsule material are shown in table 3. FIGURE 5. Cross section of heat storage capsule with PCM. TABLE 2 The dimension of heat storage capsule and weight of PCM Table 3 Properties of the PCM and the capsule material
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