Problems and solutions to non-mechanical refrigeration insulation boxes using dry ice as cold source

Although there are many advantages to insulating boxes using dry ice as a cold source, the sublimation of dry ice can easily cause frost; the insulating box can easily deform when dry ice is cooled; and too much carbon dioxide will cause refrigerated items such as fruits and vegetables to have difficulty breathing and become necrotic. It is difficult to adjust the temperature inside the box. Countries are still in the experimental development stage. There are still several problems in the following aspects before it can be put into practical application.

(1) Insulation box body design

At present, the box structure and insulation materials of my country's thermal insulation boxes should comply with relevant standards, and the heat transfer coefficient of the thermal insulation box should be controlled within a certain range. Considering the production cost, manufacturers generally use rigid polyurethane or other advanced insulation materials with excellent thermal insulation properties as the insulation layer. However, the vaporization temperature of dry ice is low, and its heat leakage is higher than other refrigeration methods with the same insulation performance. Therefore, the thermal insulation performance of the insulating box directly determines the consumption of dry ice and the utilization rate of the box volume. This requires the insulated box to have better thermal insulation performance.

One method of improvement is to improve the insulation performance of the insulation layer, which can be achieved by thickening the insulation layer or using more advanced insulation materials. Studies have shown that the use of high-efficiency insulation materials such as VIPs (vacuum insulation panels) can greatly improve the insulation performance of the incubator.

In addition, the sublimation of dry ice will produce a large amount of gas, which will put the inside of the box at a positive pressure. The amount of gas leakage inside the insulated box will also increase accordingly, taking away a large amount of cold energy, resulting in an increase in dry ice consumption. If rotational molding technology is used, one-piece molding and uniform wall thickness can improve the sealing performance of the box. This type of insulated box needs to have higher air tightness to reduce gas leakage and cooling loss and not be easily deformed.

(2) Control of temperature inside the box

Each type of food has specific refrigeration temperature requirements, and food should always be kept in a suitable refrigerated environment during transportation. However, due to the lower temperature of dry ice, the temperature difference cannot be controlled inside the incubator. Although this has little impact on the transportation of frozen food, it may not be able to meet the requirements for some fruits and vegetables that have a small refrigeration temperature range and are prone to spoilage. Therefore, new temperature control measures need to be studied, such as temperature control design, adding temperature monitoring points, etc., to improve the stability and uniformity of temperature control in the box.

(3) Food contamination in the box

Although CO2 is a harmless gas for most foods, some foods are not suitable for storage in high-concentration CO2 environments. For example, the surface of bananas, cabbage and other foods may turn black in a high-concentration CO2 environment, affecting the appearance quality. Therefore, incubators using dry ice as a cold source must be designed with appropriate cooling methods to avoid food contamination. You can consider using indirect cooling, that is, letting the CO2 gas cool the air first, and then cooling the food through the air, thereby avoiding direct contact between the CO2 gas and the food.

(4) Utilization rate of the volume inside the box

During the transportation of the incubator, the required dry ice is stored in the storage room of the incubator in the shape of snowflakes. Due to the large consumption of dry ice, the storage room will occupy a certain volume. If long-distance transport is planned, dry ice will require greater storage space, which may result in reduced effective volume utilization of the insulated box.

In order to improve volume utilization, consider designing the dry ice storage room into a retractable container. This container automatically adjusts in size based on the actual dry ice storage capacity, ensuring adequate dry ice storage without wasting space. At the same time, this retractable container also needs to have a certain pressure-bearing capacity to adapt to different evaporation pressure requirements.

ICECON specializes in a series of rotational molding boxes such as constant temperature (cold and hot) boxes and dry ice insulated boxes. During refrigerated transportation, our company has a variety of insulation methods such as cold storage panels, dry ice and CO2 for you to choose from.our products have obtained prestigious certifications such as ISO9001, NSF, and CE, attesting to their exceptional quality and reliability.