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A novel heat pump drying system with auxiliary solar source and ejector using a variable speed compressor has been experimentally investigated. The influences of compressor speed on the performances of novel system were comprehensively evaluated and compared to the basic heat pump drying system. Moreover, the relationship between the compressor speed and the drying temperature under different solar radiation intensity was clarified. The experimental results indicated that the novel system achieved the higher heating capacity and drying temperature because of the input solar energy. However, the excessive heat input to the drying system also would increase the electrical consumption. To solve this problem, the novel system using a variable speed compressor could obtain the same drying temperature as the basic system at the lower compressor speed. When drying at the same temperature of 70 °C, compared to basic system, the novel system using a variable speed compressor improved the moisture extraction rate by 6.8 %–22.4 %, the specific moisture extraction rate by 23.7 %–31.4 %, and the COP by 26.5 %–42.3 %. The results could provide the guidance for combining the variable speed compressor and the heat pump drying system with auxiliary solar source. [ABSTRACT FROM AUTHOR]

Recently, heat pump technology has become the preferred method in drying field. However, most existing heat pump cycles use the single-stage vapor compression with expansion valve, which has the problem of large throttling loss. The use of ejector in the heat pump cycle can recover part of the expansion work and enhance cycle performance. Therefore, this paper proposes a solar-enhanced ejector expansion heat pump cycle (SEEHP) for drying application. Based on the conventional ejector expansion heat pump cycle (EEHP), the introduction of solar energy could not only improve the heating capacity of the cycle, but also improve the performance of the ejector. The energy, exergy and economic evaluation methods are used to theoretically analyze the EEHP and SEEHP. Compared to the EEHP, the energy analysis shows that the SEEHP with R134a refrigerant has a 23.64%–39.82% increase in heating coefficient of performance (COP h) and 32.79%–33.96% increase in volumetric heating capacity (Q cv) for the given condensing temperature range. Exergy analysis results reveal that the exergy destruction of SEEHP is mainly concentrated in the solar collector, indicating that the solar collector has the greatest potential for optimization in practical application. Economic analysis shows that investing in solar energy in the SEEHP is beneficial. [ABSTRACT FROM AUTHOR]

This research aims to explore a novel PCM that can satisfy the needs of vaccine cold chain logistics temperature zone (2–8 °C), with decyl alcohol (DA) and lauric acid (LA) chose to be eutectic. Considering the thermal conductivity and leakage of materials, DA-LA/EG composite phase change material (CPCM) with a mass ratio of 12:1 is prepared by the vacuum adsorption method. The thermal properties of DA-LA/EG CPCM are analyzed by DSC, cooling curve, Hot Disk, SEM etc. From the DSC graphs of DA-LA eutectic phase change material (EPCM), it is found that there is difference between the melting temperature and solidification temperature, which is defined as phase change hysteresis. The results indicate that the phase transition temperature of DA-LA/EG CPCM is 2.08 °C, with high latent heat and thermal conductivity of 188.71 J g−1 and 1.7527 W m−1 K−1, respectively. Due to the unique porous structure of EG, the thermal conductivity is 13.75 times higher than that without EG, which leads to the phase transition time shortened by 79.47%. Furthermore, DA-LA/EG CPCM shows excellent cyclic stability and chemical stability after 500 high-low temperature alternating tests. From TGA, the decomposition temperature of DA-LA/EG CPCM is 186.55 °C, higher than the working temperature range. The applicability is demonstrated by using the CPCM into an incubator. Overall, DA-LA/EG CPCM has good application prospects in vaccine cold chain logistics. [ABSTRACT FROM AUTHOR]