Experimental Study and Energy Evaluation of Heat Pump–Solar Hybrid Drying of Bitter Melon
Nguyen Thi Viet Linh1, Pham The Vu2, Nguyen Ngoc Quy3
1Nguyen Thi Viet Linh, Faculty of Energy Engineering, School of Electrical and Electronics Engineering, Hanoi University of Industry, Hanoi, Vietnam.
2Dr. Pham The Vu, Department of Energy, School of Electrical and Electronics Engineering, Hanoi University of Industry, Ha Noi. Vietnam.
3Nguyen Ngoc Quy, Department of Energy, School of Electrical and Electronics Engineering, Hanoi University of Industry, Ha Noi. Vietnam.
Manuscript received on 04 June 2025 | First Revised Manuscript received on 13 June 2025 | Second Revised Manuscript received on 16 July 2025 | Manuscript Accepted on 15 August 2025 | Manuscript published on 30 August 2025 | PP: 1-5 | Volume-5 Issue-5, August 2025 | Retrieval Number: 100.1/ijpte.E202805050825 | DOI: 10.54105/ijpte.E2028.05050825
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© The Authors. Published by Lattice Science Publication (LSP). This is an open access article under the CC-BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Abstract: This study experimentally investigates the performance of a hybrid drying system that integrates a heat pump with solar thermal energy, aiming to improve energy efficiency in the drying of bitter melon (Momordica charantia). The research focuses on the effects of slice thickness on drying time, Specific Energy Consumption (SEC), and the quality of the dried product. Drying trials were conducted using slices of bitter melon of three different thicknesses: 1 mm, 2 mm, and 3 mm. The hybrid system employed a flat-plate solar collector to preheat the inlet air before it entered the heat pump drying chamber. Results show that slice thickness had a significant effect on drying kinetics. Slices with 1 mm thickness reached the target moisture content in 4 hours, whereas 3 mm slices required up to 5.5 hours. The integration of solar preheating reduced total electrical energy consumption from 4.3 kWh to 2.7 kWh per batch, yielding an energy savings of approximately 37.2%. The SEC was also reduced, from 5.73 to 3.60 kWh/kg of evaporated water. In addition to energy improvements, the hybrid system helped retain favourable product characteristics, including a final moisture content of 10–12%, natural green colour, aroma, and essential bioactive compounds such as momordicin and flavonoids. These outcomes demonstrate the hybrid system’s potential as a sustainable solution for smallto medium-scale agricultural drying. A slice thickness of 1–2 mm is recommended for optimizing both drying efficiency and product quality. The findings support further research on the drying parameters that affect nutrient retention and the physical properties of dried agricultural products.
Keywords: Bitter Melon Drying; Hybrid Drying System; Solar Energy; Heat Pump; Drying Kinetics; Energy Efficiency; Product Quality.
Scope of the Article: Solar Systems