How does isothermal bag (portable refrigerator)

People sometimes are puzzled by a compact cooler bag: how does this household appliance work, even if not every model has a wire for connecting to the network? But the cosmetics on the summer beach, and a bottle of water, and a jar with baby food or sandwiches for a picnic are perfectly preserved in a convenient backpack or bag. The cooler bag can be connected to the car power grid on a long trip, and use it offline if there is no car. At the same time the device of a refrigerator bag depends on its model.

Not all portable refrigerators are the same.

In fact, only one type of cooler bag can be recognized as a reduced copy of an ordinary home freezer. Most often they work on a completely different principle, conditionally they can be divided into 3 main varieties:

• keeping temperature;
• supporting heat or cold;
• actively cooling.

Virtually all models of portable refrigerated containers can also be used as thermoses, which retain not only cold but also heat. You can take a cooler bag with you for a winter walk to pamper yourself and your friends hot, piping hot, pies or pizza. There is no magic here: this possibility is conditioned by the device of these portable thermal containers.

How does a thermos bag work?

A plastic container, a backpack or a bag made of bright synthetic is very convenient for those who go on a journey on foot. The advantage of the bag compared to the container is indisputable: it can be rolled up when it is empty. But the container itself can serve as a convenient container for other things when not used for its intended purpose.

The principle of operation of such devices is simple: they are large-sized thermoses in which you can store hot or cold food. The bag (or backpack) consists of 2 layers of nylon fabric, between which a layer of foamed polyurethane or polyethylene is placed. These materials retain well the temperature inside the tank, plastic and light. Hypoallergenic and no smell make them suitable for use as a container for food.

The temperature inside this refrigerator does not change for several hours.

Thermal container consists of 2 plastic containers. The space between the walls of the outer and inner boxes is filled with isothermal material. Most often it is foam (polyurethane foam, polystyrene foam). A layer of foam has a container lid, which makes it airtight and fully meets the task of maintaining the desired temperature of the contents. The thickness of the insulator can reach 4 cm, and this makes it possible to keep the temperature unchanged up to 15 hours.

Simple cold storage is not all that portable thermal containers are capable of. Some of them can maintain the desired temperature inside the tank, which almost 2 times increases the duration of their work. These are cooler bags with cold or heat accumulators. They differ from previous models by the presence of special containers filled with saline, gel or dry ice.

The tightness of the battery allows you to keep the amount of the active substance unchanged and use them repeatedly.

Battery cold with dry ice manufacturers recommend putting in the freezerdomestic refrigerator for 1.5-5 hours before use. The term of freezing depends on its volume. A prepared battery should be placed in a cooler bag and filled with pre-cooled products. Thawing, dry ice will absorb heat, keeping it cool inside the container. After application, it is recommended to rinse the surface of the battery and store it in a dry place. If the need for a cold accumulator occurs frequently, then it can be stored right in the freezer, so it will always be ready for use.

Some types of thermo-accumulators can support and heat inside the insulated bag. To do this, they need to be kept in hot water before use in accordance with the manufacturer's instructions. To maintain the desired temperature inside the bag you need 1 battery per 5 liters of volume. If desired, you can purchase a separate container with gel or solution to increase the duration work refrigeration bags.

Real fridge

All types of thermal containers with connection to the automobile electrical network can be attributed to this group. You can connect them through the cigarette lighter socket, for this the cord has a special connector.

Some models of absorption mini-refrigerators can work on propane or butane, then they will need to purchase an additional cylinder with gas.

Gas varieties are very convenient for use away from civilization, but require a nearby gas station or store where you can buy gas. Their disadvantage is that a fairly bulky 5-liter bottle is only enough for 8 days of work. The principle of operation of such refrigerators is based on raising the temperature of the working solution by a gas burner.

Compression and thermoelectric cooler bags are the closest in principle to a classic refrigerated cabinet. They do not just keep the temperature inside the airtight container, but also actively cool the air in it. A small 12V mains compressor pumps refrigerant (isobutane or freon) into a thin tube system, where the gas heated from the compression quickly cools to ambient temperature. Through a very thin capillary gas enters the evaporator tubes located inside the bag or container. Expanding there, it takes a significant part of the heat from the environment, and cool air helps to reduce the temperature of the products placed in an isothermal tank.

The disadvantage of the compression cooler bag is its increased sensitivity to shocks and vibrations. They are inevitable when moving even along the most even line and lead to disturbances in the operation of compression isothermal equipment.

Modern thermoelectric refrigerated containers and bags work on a completely different principle. In the cooling unit of such devices there are neither liquids nor gases. The principle of operation is based on the Peltier effect: at the junction point 2 of semiconductor materials with the passage of current intensive absorption of heat occurs. At the same time, the Peltier element cools itself very much and takes away some of the heat from the air in the bag.

The power supply of such isothermal capacity can be carried out both permanently, from the automotive network, and autonomously, from the battery built into the container. Charging it can be carried out from the mains in 12 V (via the cigarette lighter socket in the car) or from the mains through a regular outlet. As a rule, such isothermal devices are marked with TEC.

Choosing a portable refrigerator, you need to determine for what purpose it will be used.There are many options for such products that differ in capacity and principle of operation. Before investing money in purchasing a cooler bag, you need to decide whether it is planned to store cool food for a picnic in it or if the device requires intensive cooling of the contents for a long time.