Experimental investigation on thermophysical properties of coconut oil and lauryl alcohol for energy recovery from cold condensate

摘要

Effective use of available energy from air conditioning condensate in a typical cold storage plant is studied. The condensate quantity was estimated for a 17,580 kW cooling capacity at around 150 to 170 liters per day at an average temperature range of 9 degrees C to 11 degrees C. Two eco-friendly phase change materials, namely coconut oil and lauryl alcohol were used to recover energy from the cold condensate. Thermophysical properties of selected phase change materials were studied for both pure samples as well as for samples after 250 cycles. Fourier-Transform Infrared Spectroscopy results confirmed that no chemical reaction took place during and after the thermal cycling and that the PCMs were chemically stable even at 250 cycles. Latent heat of fusion of coconut oil and lauryl alcohol decrease by 10.55% and 52.9% respectively after 250 cycles. The variation in specific heat capacity and thermal conductivity at working range temperatures were observed before and after the thermal cycles and the results are discussed. The charging and discharging studies of PCMs (1 kg each) were carried out at 11 +/- 1 degrees C using a constant temperature water bath with a holding volume of 12 liters. The solidification was found to start at 22.3 degrees C for coconut oil and 23.1 degrees C for lauryl alcohol. During the solidification, it was found that coconut oil was supercooled from its actual freezing temperature by 2.6 degrees C. Due to this supercooling effect, the actual freezing time is prolonged by 25 min for coconut oil. However, no supercooling was observed in lauryl alcohol. Discharging of PCMs was carried out in an ambient environment of 32 +/- 1 degrees C. Melting study revealed that coconut oil and lauryl alcohol were melting at 23.2 degrees C and 23.8 degrees C respectively, which is almost equal to the human comfort temperature of 24 degrees C. However, considering the ecofriendly nature, thermal stability and material compatibility, coconut oil could be a better option compared to lauryl alcohol and other organic PCMs.