Scientists from the Institute of Thermal Science and Technology (Hanoi University of Science and Technology) have successfully developed a modular heat pump for dehumidification and cold drying. This is the first time such equipment has been successfully manufactured domestically, proving highly useful for agricultural product preservation.
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| Harvested agricultural products need to be properly preserved |
Vietnam is located in a tropical, humid climate with a coastline of over 3,000 kilometers, where humidity often exceeds 70%, and temperatures can rise above 38oC. The hot and humid climate creates favorable conditions for the growth of mold and harmful microorganisms, which damage many food items, medicines, and crop seeds.
This situation is particularly critical for an agricultural country like Vietnam, which still has outdated scientific and technological practices. In many localities, due to a lack of proper equipment for preserving fruits and agricultural products after harvest, products often have to be sold at drastically reduced prices, sometimes only achieving 20% of their actual value.
Traditionally, drying products has involved using hot air (with temperatures ranging from 60oC to 120oC), while dehumidifying is typically done using dehumidifiers that operate on a heat pump principle.
In the treated space, reducing humidity with a dehumidifier requires maintaining a temperature higher than that of the environment, resulting in relative humidity not dropping below 55%, especially when outdoor humidity levels are usually between 80% and 90%.
Until now, dehumidification and cold drying have often relied on imported machinery and equipment. These machines are not only expensive but also fail to maintain performance during high humidity days, leading to reduced product yield and quality. There have even been instances where imported systems required additional domestic dehumidifiers to ensure continuous and stable production. Additionally, some costly imported devices consume a lot of energy but only operate for short periods under hot and humid conditions, failing to meet technical specifications.
After years of research, a team of scientists from the Department of Refrigeration and Air Conditioning at the Institute of Thermal Science and Technology, led by Associate Professor Pham Van Tuy, successfully designed and manufactured a modular heat pump for dehumidification and cold drying as part of a ministry-level scientific research project titled “Research on Dehumidification and Cold Drying of Vegetables and Food.”
The researchers proposed a new technological solution: instead of using two separate devices for dehumidification and drying as per traditional methods, a single refrigeration unit can be utilized for both dehumidifying and low-temperature drying. This marks the first time that a dehumidifier and cold drying machine for agricultural products, food items, and medicinal herbs have been designed and manufactured domestically, offering a reasonable cost with high economic and technological efficiency.
In terms of economic efficiency, the multifunctional dehumidifier and cold drying system boasts several advantages: it saves on capital investment. The cost is only 50% compared to similar imported equipment. A 60 kW cooling system, operating at 20oC – 27oC with 35% – 45% humidity, costs 300 million VND. A 35 kW cooling system (120,000 BTU/h) is priced at 250 million VND.
By replacing separate refrigeration and dehumidifying machines with a combined refrigeration and air conditioning system that has been modified into a heat pump, energy consumption has decreased from 17.5 kW (for the old system) to 11.4 kW. After many years of operation, the equipment continues to function safely and effectively, suitable for Vietnam’s hot and humid climate.
The project is poised for widespread application and development in the preservation of agricultural products, food, fruits, and medicinal herbs after harvest, as well as for dehumidifying environments for export production, replacing imported products for post-harvest technology in Vietnam.
The project has completed six contracts for scientific research and cooperation with various research facilities, including Hai Ha Confectionery Company in Hanoi, Viet Tri Food Factory, the Food Technology Institute, and the Hanoi Food Center.
It has been awarded the “Patent of Invention” and the Vietnam Science and Technology Innovation Award (VI FOTEC) in 2003, with Associate Professor Pham Van Tuy receiving a “Creative Labor Certificate.”
Not stopping there, the scientific team has been conducting in-depth research to enhance the economic-technical indicators, compactness of the equipment, and adaptability to various product types.
As one of seven projects at the university upgraded to a “Technology Incubation” project in 2005, this project has successfully designed, manufactured, and implemented a multifunctional dehumidifier and cold drying system in the form of a low-temperature heat pump branded as HUST BK-BSH 18, which has been installed at the Viet Tri Food Factory.
