The insulation principle of cold storage bags
The insulation performance of the cooling bag depends on the synergistic effect of multi-layer composite structure and thermodynamic mechanisms, the core of which is ``blocking heat transfer ''.
Insulation Material Structure
1.Outer layer: Usually made from 600D Oxford cloth or engineering plastics (such as PP or LLDPE), it is shock, UV and abrasion resistance, protecting internal structures from physical damage.
2. The intermediate layer is made of pearlescent foam (EPE) and aluminum foil. This layer is important for insulation. The EPE's closed-cell construction prevents air flow and heat from passing through. The aluminum foil's high reflectivity (over 95%) prevents radiation heat transmission, creating a "heat-reflecting barrier."
3.Inner layer: Made from food-grade eco-friendly materials such as PEVA or TPU, it is nontoxic and odorless, preventing condensation infiltration and contamination while maintaining temperature stability.
Thermodynamic mechanism
The insulation effect of cold bags is based on the following thermodynamic principles:
Aluminum foil's smooth surface reflects infrared radiation, reducing the amount of heat that radiates into the bag.
EPE Styrofoam insulation: Its enclosed structure prevents air from passing through it, slowing the flow of heat through convection. The material has a low thermal conductivity of about 0.034 W// (m.K), making it difficult for heat to pass through.
Sealed design: two-way zipper or magnetic structure to keep the seal tight, keep the interior cool, prevent temperature rise, prevent air leakage.
Conditions for achieving good thermal insulation effect
Pre-cooling
Ice bags or ice blocks are "cooling sources" of coolants, and their precooling directly affects their insulation duration:
Freezing Temperature and time: Coolers must be refrigerated for at least 24 hours in an environment between -20°C and -40°C to ensure complete crystallization and maximum cooling capacity of internal phase transition materials (e.g. PCM). If not completely frozen, the bag may melt prematurely, damaging insulation.
·Ice Pack Type: Reusable ice packs (such as Tech Ice) are made of high-molecular-weight polymers and have a cooling capacity six times that of regular ice. They also release cold air more evenly, extending the storage duration of the freezer.
Controlling the temperature of the environment
High temperatures: In the summer, while the sun is shining, the temperature outside can reach over 40 degrees Celsius, which speeds up the absorption of heat through the outer layers of cooling bags. Every time the interior temperature goes up by 10°C, the respiration rate (the rate at which heat is exchanged) goes up by 2 to 3 times, which makes insulation last a lot less time. Low temperatures: In the winter, low temperatures can slow down the melting of ice packs and make them last longer. However, you should be careful not to let ice build on things inside, such medicines and fresh food, because this could hurt them.
Sealing and Load Management
1.Seal: Loose zippers can cause cold air to leak. It is recommended to check the seal before use and avoid opening and closing plastic bags frequently.
2. Load Management: Overcharging compresses insulation and reduces thermal performance. Inadequate filling increases internal air convection and accelerates temperature fluctuations. Bags are recommended to be between 70% and 80% full.
How long does the cold storage bag last?
1.Normal Ordinary Cooler Bags: These air bags utilize a layer of aluminum foil and foam and usually stay warm for 2-12 hours. the Yikule brand, for example, claims its products keep food cold for 12 hours and hot for 6 hours, making them suitable for short trips or everyday use.
2. Professional cooler bags can keep things warm for 24 to 120 hours by using layers of insulation (such vacuum, aluminum foil, pearl, etc.) and big ice packs. Often used in medicine that has to stay cold or for long-distance travel.
1. Quality of the ice pack: Tech Ice and other high-performance ice packs have a lot of cooling power and cool evenly, which keeps the heat in for 30% to 50% longer.
2. Ambient Temperature: High temperatures (over 35 degrees Celsius, for example) can cut the time it takes to keep heat by more than 50%, while low temperatures (under 10 degrees Celsius, for example) can add 20% to 30% to the time it takes to keep heat.
3. The starting temperature of the items: Pre-cooling things like refrigerated food can lighten the strain on the ice pack and make cryopreservation last longer. Putting hot food directly on an ice pack can make it melt faster and make the ice pack less effective at keeping things cold.
Conclusion: Practical value and recommendations of Cooler Bags
Through the innovation of materials science and structure design, High-quality cooler bagachieves efficient insulation. They can be used for many things, such as short trips, outdoor activities and medicinal cold chains. When choosing a cold bag, the average user should consider the following:
1.Choose the right time to use it according to your needs. For everyday use, consider using a tote bag for 2-12 hours. Consider using a tote bag for longer than 24 hours when using it long distance.
2.Choose the proper material according to the method of use. For example, aluminum foil booster bags are good for outdoor activities because they are abrasion-resistant. Basic foam bags are a better option for food delivery because they're cheaper.
3.Attention to detail: ice pack pre-cooling, indoor temperature control, temperature not too high, can make the insulation effect better.
Sources cited
- Baidu Encyclopedia: "Cold Storage Bags": Material structure, insulation duration data, and industry standards.
- WeChat Public Platform: "3 Minutes to Understand - Ice Bags": Ice bag pre-cooling principles and phase change material properties.
- Taobao: "Ice Cream Won't Melt the Next Day? Uncovering the Insulation Principle of Aluminum Foil Insulated Bags": Aluminum foil's heat reflection principle.
- Douyin: "Ice Coke I Put in the Morning Is Still Ice Cold by the Evening! This Export Insulated Bag is Really Excellent": A case study of the insulation duration of the Yikule brand.
- Beijing Zhongke Optical Analysis Chemical Technology Research Institute: "Refrigerant Box Ice Pack Insulation Duration Verification": Ice pack pre-cooling temperature and time requirements.
- WeChat Public Platform: "Film Packaging for Refrigerated Freshness of Fruits and Vegetables": The impact of ambient temperature on insulation performance.
- Baidu Encyclopedia: "Low-Temperature Freshness Ice Packs": Performance comparison of reusable ice packs.
