Comprehensive assessment of heat pump dryers for drying agricultural products

Abstract

Fruits and vegetables are agricultural products that require preservation to enhance and protect shelf life, encapsulate natural flavour, and retain nutritional content. Globally, agricultural products are preserved by a range of means, the most prevalent of which is the heat pump dryer, which produces the best results even in unfavourable climatic conditions. Heat pump dryers come in different types and their performance varies depending on the type. This study aims to evaluate recently developed heat pump dryers based on key performance indicators, impacts on food colour and nutritional content, techno‐economic, exergoeconomic, and environmental issues associated with the development of heat pump dryers, which are underrepresented in most of the existing heat pump dryers' reviews. This study also discusses mathematical drying kinetic models, and regulation or policy aspects related to the development of heat pump dryers. In the present study, the results on performance analysis indicate that heat pump dryers examined were effective in reducing drying time and obtaining high coefficients of performance ranging from 1.94 to 5.338 and specific moisture extraction rate ranging from 0.156 to 9.25 kg/kWh, as well as significantly reducing energy consumption by up to 80%. The nutritional composition and colour results show that heat pump dryers maintain the maximum nutrient content while also improving colour. The expansion valve has the lowest exergoeconomic factor of all heat pump dryer components, whereas the compressor has the highest cost of exergy destruction in general, according to the results of exergoeconomic analysis. Techno‐economic analysis results demonstrated that most developed heat pump dryers have short payback periods ranging from 1.6 to 3.6 years. However, due to a lack of research in this field, the environmental implications of heat pump dryers are unknown. As per the findings of this study, future research in this field should focus on the design of simple and low‐energy heat pump dryers, life cycle, techno‐economic, and exergoeconomic assessments.

Techno‐economic analysis of a solar‐assisted heat pump dryer for drying agricultural products

“…The SMER of 1.33 kg/kWh in this study is within the range of 0.156–9.25 kg/kWh reported by Loemba et al. ( 2022 ) for most of the heat pump dryers. The COP was calculated from Equation 8 and found to be 3.4, and the thermal efficiency was calculated from Equation 9 and found to be 54.0%.…”

“…The COP was calculated from Equation 8 and found to be 3.4, and the thermal efficiency was calculated from Equation 9and found to be 54.0%. The COP obtained from this study is within the range reported by Loemba et al (2022) during the compressive assessment of heat pumps for agricultural products, in which it was reported that most of the heat pumps have COPs ranging from 1.94 to 5.38. The thermal efficiency of SAHPD obtained in this study is in agreement with the 56.69% reported by Singh et al (2020b) in Table 4B during the application of SAHPD for the drying of banana chips.…”

“…The SMER was calculated from Equation 7 and found to be 1.29 kg/kWh for tomatoes and 1.33 kg/kWh for carrots. The SMER of 1.33 kg/ kWh in this study is within the range of 0.156-9.25 kg/kWh reported by Loemba et al (2022) for most of the heat pump dryers.…”

“…SAHPD can function successfully throughout the day, even when there is no sunlight, assuring the quality of the dried products (Gan et al, 2017). Loemba et al (2022) conducted a comprehensive assessment of heat pumps for drying agricultural products and reported that using heat pumps significantly reduced drying time, improved specific moisture extraction, and reduced energy consumption.…”

“…Loemba et al. ( 2022 ) conducted a comprehensive assessment of heat pumps for drying agricultural products and reported that using heat pumps significantly reduced drying time, improved specific moisture extraction, and reduced energy consumption.…”