ABSTRACT
Air conditioning (AC) systems for tropical countries like India account for sixty percent of the total energy needs of a building. With the onset of COVID-19, the increase of fresh air ventilation rate has been recommended by various guidelines for indoor spaces which increase the load on the AC system. The present study attempts to reduce this burden through retrofitting a phase change material (PCM) embedded pin fin heat exchanger into an air-conditioning system. The heat exchanger is designed to cater to the peak load fluctuations for cities in three hot climatic zones of India, viz., Jaisalmer, Kolkata, and Delhi. Dodecanol with a melting temperature of 24 degrees C, is chosen as the appropriate PCM material for these locations. The optimal pin fin diameters are estimated through an entropy generation minimization analysis for the three locations. A heat transfer analysis of the PCM embedded heat exchanger is further presented through an analytical approach to estimate the PCM mass requirement and energy savings potential. The masses of the PCM estimated for Jaisalmer, Kolkata, and Delhi are 11.36 kg, 22.42 kg, and 19.35 kg, respectively for their respective peak load fluctuations of 0.25 kW, 0.28 kW and 0.48 kW. Energy savings of up to 4.7 % for Delhi, 2 % for Kolkata, and 2.75 % for Jaisalmer are identified with the PCM embedded heat exchanger incorporation. The results show the potential of such PCM thermal storage in reducing the peak energy demands of buildings amidst various environmental and health concerns.
ABSTRACT
Solar Air Heater (SAH) technology as a drying method for agricultural commodities is only active during the day and is highly dependent on the weather. Therefore, this study aims to investigate the effect of SAH coupled with phase change material (PCM) types of paraffin wax, soy wax, and palm wax as store energy materials to enhance the performance of conventional SAH. The PCM containers placed in the SAH are ex-bottles of milk cans which are numerous in the country due to the increase in consumption of milk by the people as an immunity enhancer during the Covid-19 pandemic. This is expected to improve the 3R (Reduce, Reuse, Recycle) strategy implemented to reduce environmental pollution. The tests conducted showed that the three types of PCM effectively improved the performance of SAH in drying agricultural commodities. The highest energy efficiency was achieved with paraffin at 30 %, 23.28 %, and 33.67 % while the highest exergy efficiency was achieved with palm wax at 20.27 %, 18.86 %, and 28.96 %, in three days respectively at different solar irradiation conditions.
ABSTRACT
Wearing Personal Protective Equipment (PPE) is essential to protect healthcare workers during the COVID-19, but the traditional cooling methods do not meet the requirements of epidemic prevention during the COVID-19. Therefore, the cooling clothing integrated with phase change material (PCM-CC) was proposed for healthcare workers performing nucleic acid sample collection outdoors. Human experiments and subjective questionnaires were used to test the effect of wearing PCM-CC on the thermal sensations of healthcare workers and to analyze the effectiveness of PCM-CC in relieving thermal stress and thereby, improving the thermal comfort of healthcare workers. Results showed that wearing PCM-CC was effective in alleviating various heat symptoms associated with wearing PPE in a hot-temperature environment. Wearing PCM-CC reduced head and facial discomfort by 25% and 41% under the 26 °C thermal environment, while it improved the mean thermal sensation vote (TSV) values by 0.71 and 1.85 under the 26 °C and 32 °C thermal environments, respectively, and made the mean TSV value close to the neutral value. Meanwhile, wearing PCM-CC reduced mean skin temperatures by 0.65 °C, and the pronounced cooling effect was found in the chest. Wearing PCM-CC could be an effective thermoregulation measure to refine the thermal comfort of healthcare workers during the COVID-19 pandemic.
ABSTRACT
Packaging is one of the most important factors affecting the overall cold chain efficiency. This paper aims to examine the current trends of cold chain packaging by conducting a comprehensive review on the current commercially available cold chain shipping solutions. A conceptual model of the cold chain shipping solutions including the structure, categories and components is proposed to provide analytical comparisons with the existing literature. It is found that the shipping solutions can improve the overall cold chain performance in many aspects which include improving temperature control performance, flexibility, safety, sustainability and knowledge sharing of the cold chains. Despite all the advantages, there are still limitations and challenges posed which are also discussed. This is the first paper presenting an overview of commercially available cold chain shipping solutions. It not only contributes to the literature by presenting new knowledge but is also beneficial for all the stakeholders in cold chain packaging by providing practical information and guidelines.
ABSTRACT
Air conditioning (AC) systems for tropical countries like India account for sixty percent of the total energy needs of a building. With the onset of COVID-19, the increase of fresh air ventilation rate has been recommended by various guidelines for indoor spaces which increase the load on the AC system. The present study attempts to reduce this burden through retrofitting a phase change material (PCM) embedded pin fin heat exchanger into an air-conditioning system. The heat exchanger is designed to cater to the peak load fluctuations for cities in three hot climatic zones of India, viz., Jaisalmer, Kolkata, and Delhi. Dodecanol with a melting temperature of 24 °C, is chosen as the appropriate PCM material for these locations. The optimal pin fin diameters are estimated through an entropy generation minimization analysis for the three locations. A heat transfer analysis of the PCM embedded heat exchanger is further presented through an analytical approach to estimate the PCM mass requirement and energy savings potential. The masses of the PCM estimated for Jaisalmer, Kolkata, and Delhi are 11.36 kg, 22.42 kg, and 19.35 kg, respectively for their respective peak load fluctuations of 0.25 kW, 0.28 kW and 0.48 kW. Energy savings of up to 4.7 % for Delhi, 2 % for Kolkata, and 2.75 % for Jaisalmer are identified with the PCM embedded heat exchanger incorporation. The results show the potential of such PCM thermal storage in reducing the peak energy demands of buildings amidst various environmental and health concerns.
ABSTRACT
With the rapid development of information technology, the concept of e-commerce has entered thousands of households, especially since the outbreak of COVID-19, fresh products are sparing no effort to join the trend of online shopping. This paper mainly summarizes phase change materials' application and development prospects in fresh e-commerce cold chain logistics. By introducing the basic conditions of phase change temperature, heat conduction, and shape of organic phase change materials, inorganic phase change materials, and composite phase change materials, the advantages of composite phase change materials are compared. The practical application progress of composite phase change materials in the fresh e-commerce cold chain logistics process is reviewed. Composite phase change materials are widely used in “storage” and “last mile” in the cold chain logistics process of fresh e-commerce, and their application in pre-cooling and transportation will be the future research direction.
ABSTRACT
This work demonstrates a self-powered wireless IoT sensing system driven by daily ambient temperature energy harvesting. A novel approach using a thermoelectric generator (TEG) which harvests thermal energy from daily ambient temperature fluctuations into electricity as a power source for wireless IoT devices is proposed and investigated. A harvested temperature difference across the TEG is created by employing a phase change material (PCM) which allows the temperature value to be maintained near the melting point at the phase transition during the ambient temperature fluctuations. Experimental results indicated that the harvested temperature differences are 10 degrees C and 5 degrees C for 300 ml and 30 ml of PCM, respectively, during the ambient temperature variations from 5 degrees C to 25 degrees C. By utilizing the ambient temperature fluctuations between day and night times, an average maximum output power of TEG measured for 3 days is 340 mu W and DC-DC electronic conversion efficiency is 28.3%. The total storable energy of approximately 1.46 J for a day is estimated. A capacitor as an energy storage unit could be fully charged and its usable energy is calculated at 0.686 J. The current consumption of 2.1 mu A for every transmit cycle is estimated. A self-powered wireless IoT sensing system driven by realistic ambient temperature variations able to sense the ambient temperature as well as the ambient humidity and transmit to a computer via RF communication is demonstrated successfully.
ABSTRACT
Globally, humanity is at risk from the coronavirus disease (COVID-19). To address the shortage of beds in quarantining those infected with COVID-19, hospitals have prepared temporary beds. However, for temporary hospital beds, it is difficult to maintain a comfortable temperature due to lack of insulation and heat storage. Phase change materials (PCMs) are used to provide temperature stability and control for temporary structure. Therefore, this study aimed to conduct experiments that analyze the effect of room temperature stabilization using a PCM. The method of macro packed PCM (MPPCM) was used to apply the PCM to buildings. The MPPCM installation location was selected and the effect of reducing the box temperature was analyzed, according to the strength of the heat source. As a result, a maximum reduction of 4.9 °C in the box temperature was achieved. Therefore, the application of MPPCM to buildings give to stabilize the box temperature. And the result showed the possibility of providing a comfortable indoor space for temporary hospital beds.
ABSTRACT
Owing to the economic recession due to the Coronavirus disease (COVID-19) pandemic, energy-efficient building retrofitting has been considered as an integrated solution to recover the economy and maintain global greenhouse gas reduction. As part of retrofitting existing building-integrated photovoltaic systems during building renovations, this study evaluated the energy generation potential of a thermoelectric generator-assisted building-integrated photovoltaic system with a phase change material. The combination of a thermoelectric generator and phase change material with photovoltaic systems results in solar cell temperature reduction and additional electricity output owing to the Seebeck effect, increasing the total generated energy from the system. Simulations of the proposed system were performed using MATLAB R2020a, based on transient energy balance equations. The appropriate melting temperature and thickness of the phase change material were derived to maximize the annual electricity generation of the proposed system from simulations of 12 design days in each month. The proposed system with the selected phase change material conditions exhibited a 1.09% annual increase in generation output and 0.91%, -1.32%, 2.25%, and 3.16% generation improvements from spring to winter, compared with the building-integrated photovoltaic system alone. Theoretically, the proposed system is expected to generate 4.47% more energy by minimizing the thermal resistance of the system and improving thermoelectric generator performance.