## 5 Conclusions  
An on-farm micro-cold storage unit is an emerging technology in cold-chain supply management. Its utility in terms of shelf-life extension and preservation of the nutritional value of the produce is beneficial to marginal farmers. However, a grid-operated cold storage unit is energy-intensive, the burden of which directly affects low-income farmers. Hence, the incorporation of phase change material is undertaken to utilize its energy-saving potential. The inclusion of thermal energy storage enhances system performance; however, the effect of its placement and selection of its encapsulation material must specifically be taken into consideration. Hence, the VCR-operated micro-cold storage unit was analyzed through numerical simulation, and the results were validated experimentally for the possible benefits of PCM integration. The following are the outcomes of this study:  
* Numerical simulation carried out using 3D experience highlighted that the temperature distribution inside the cold room varied from 26.8 \({}^{\circ}\)C to 7.8 \({}^{\circ}\)C at the beginning of the storage cycle, and the maximum heat transfer was observed in the upper zone of the cold room where the evaporator cooling effect was seen to be maximum. The mesh independence study was carried out, and it was observed that changing the mesh sizes impacted the simulation by affecting the display resolution with negligible change in temperature profile; however, the time taken for the simulation was almost 1.5 times with a higher mesh count;
* This study was also undertaken to select the appropriate encapsulation material for PCM, where copper and stainless steel were compared both numerically and experimentally. The experimental results indicated that SS offered an excess thermal resistance of 4 \({}^{\circ}\)C in comparison to copper, inferring improved cooling effect pene  
Figure 14: Comparative study of numerical and experimental methods for PCM cooling in tumbler. tration into the copper heat exchanger. Numerical simulations, as well as analytical computations, were found to be in conformity with the experimental results. The maximum cooling effect was obtained when copper containers as PCM encapsulations were positioned on the wall opposite the evaporator and its adjacent wall, providing the necessary thermal backup;
* The total energy consumption was found to be 1.1 kWh, where the maximum compressor cycle recorded was 17 min with 7 min of compressor ON-time. A steep rise in temperature was observed as soon as the compressor was stopped, highlighting the inability of a simple VCR cycle to maintain the set temperature even for a short duration of compressor OFF-time, which could be overcome by appropriate selection of PCM, its encapsulation material, and its mounting location;
* A temperature difference ranging from 5 to 7 \({}^{\circ}\)C is observed between the phase change temperature of PCM and the optimal storage temperature. This observation is important from the point of view of appropriate PCM selection. Future research is focused on examining various combinations of PCM with appropriate encapsulation material to achieve an ideal combination for desired thermal back for applications as well as sizing and optimization of the PCM heat exchanger. Conceptualization, S.A. and A.R. ; methodology, S.A. and A.R. ; software, R.J.B. ; validation, S.A. and A.R. ; formal analysis, S.A. and R.J.B. ; investigation, S.A., P.N., P.P., P.E. and V.K. ; resources, A.R. and S.L. ; data curation, S.A., R.J.B. and A.R. ; writing--original draft preparation, S.A.; writing--review and editing, A.R. ; supervision, A.R. and S.L. ; project administration, A.R. ; funding acquisition, A.R. All authors have read and agreed to the published version of the manuscript. This work is supported by Symbiosis International (Deemed) University under SIU/SCRI/MJRP/Approval/2023/1753 and Indian Society of Heating, Refrigerating, and Air Conditioning Engineers (ISHRAE) under SRPG PG 2022-23. Not applicable. Data presented in this study is available in this article.