A new cooling technology has been developed that stores the cold heat in the cold winter season and uses the cold heat stored in the summer for cultivation of facilities such as houses.
On August 30, Dr. Young-Jik Yoon's research team at the Energy Network Lab of the Korea Institute of Energy Research (President Jong-Nam Kim) announced that they had succeeded in developing a heat exchanger using bubble self-vibration that can be used to cool houses in rural areas in summer using cold heat in winter.
Self-vibration of bubbles refers to a phenomenon in which slugs including bubbles vibrate rapidly without external power when there is a temperature difference between the two sides.
The temperature in the house during the hot season approaches 50~70℃, which is fatal to crop growth. Although it relies on electric cooling equipment to prevent temperature rise, there is a limit, and high energy costs place a great burden on facility-cultivating farmers.
In particular, this year, it was more urgent to develop a cooling technology of a new concept using natural energy or eco-friendly natural cooling principle rather than electric cooling, which consumes a lot of electricity due to the increase in electricity rates due to high oil prices.
Cold heat production based on high-efficiency, low-cost heat exchange technology
Dr. Young-jik Yoon's research team succeeded in developing a high-performance heat exchange device using bubble self-vibration without using external power, opening a new era of cooling technology.
The heat exchanger developed by the research team consists of a meandering capillary tube connected to cold outside air or a cooling tank, and the refrigerant inside the tube. In addition, as a storage medium for cold air underground, water is stored in a cooling tank.
There is a difference in the temperature between the cold outside and the underground water in winter. In this environment, the internal refrigerant vibrates rapidly with the temperature difference occurring at both ends of the heat exchanger developed by the research team, and a flow occurs, and a large amount of it is delivered quickly. Through this, the heat of the underground water is radiated to the cooler outside, and the water temperature gradually decreases, and it is stored and used until summer.
Since no external power is required to operate the heat exchanger, there is no operating cost burden. In addition, since a large amount of heat can be transferred by using latent heat through phase change, energy consumption can be reduced by more than 50% and size by more than 30% compared to the existing heat exchange technology, maximizing cooling and heat production efficiency and reducing the unit cost of manufacturing equipment. It is economical because it can be saved.
Dr. Young-jik Yoon's research team installed a heat exchanger for cold heat production at the demonstration site of the Seoul National University Pyeongchang Campus in Pyeongchang-gun, Gangwon-do since last March and conducted cold-heat production and storage experiments. Through this, the result was derived that cold water of about 4.5°C was produced and stored in the underground storage tank with a capacity of 1 ton with a cooling heat production capacity of about 1 kW.
In particular, since it is a demonstration result after March, it is expected that cold water lower than 4.5℃ can be produced under lower outdoor air conditions.
Through this experimental result, the research team plans to improve the capacity and performance of the heat exchanger and demonstrate the cooling supply to a 330m² (100 pyeong) glass greenhouse in the Smart Farm Advanced Agricultural Complex of Seoul National University Pyeongchang Campus, which will be completed in October. In addition, it plans to expand to cooling and air-conditioning technologies for various consumers such as plant factory-type smart farms and city buildings.
Dr. Yoon Young-jik said, “It is important to secure high-efficiency, low-cost, renewable energy-based cooling technology to strengthen food security in response to the global climate crisis.
Meanwhile, this research was carried out with the support of the smart farm multi-ministerial package innovation technology development project and the research institute basic project jointly hosted by the Ministry of Agriculture, Food and Rural Affairs, the Ministry of Science and ICT, and the Rural Development Administration.