General knowledge of temperature and humidity management of commodity storage space

To do a good job in the temperature and humidity management of storage space, we must first learn and master the basic concepts of air temperature and humidity and related basic knowledge.

Air temperature: air temperature refers to the cold and hot degree of air. Generally speaking, the closer to the ground, the higher the temperature, and the farther away from the ground, the lower the temperature. In the daily temperature management of storage space, it is often expressed in Celsius. For degrees below 0 degrees, add a “-” before the degree, which means how many degrees below zero Celsius. If you want to record the temperature more accurately, it is recommended to use Kehao’s temperature recorder.

Air humidity: air humidity refers to the amount of water vapor in the air or the degree of dryness and wetness of the air.

It refers to air humidity. There are mainly the following methods: absolute humidity. It refers to the actual amount of water vapor contained in the air per unit volume, generally in grams. Temperature has a direct effect on absolute humidity. Generally, the higher the temperature, the more water vapor evaporates, and the greater the absolute humidity; On the contrary, the absolute humidity is small. Saturation humidity. Saturation humidity is the maximum amount of water vapor that can be contained in a unit volume of air at a certain temperature. If this limit is exceeded, the excess water vapor will condense and become water droplets. The air humidity at this time is called saturation humidity. The saturation of air is not fixed, it changes with the change of temperature. The higher the temperature, the more water vapor can be contained in the air per unit volume, and the greater the saturation humidity.

Relative humidity: relative temperature refers to the percentage of the actual amount of water vapor (absolute humidity) in the air from the saturation state (saturation humidity). That is, the percentage of absolute humidity to saturated humidity at a certain temperature. Relative humidity is expressed as a percentage. The formula is: relative humidity = absolute humidity / saturated humidity × 100%, absolute humidity = saturation humidity × Relative humidity: the higher the relative humidity is, the wetter the air is; The smaller the relative humidity is, the drier the air is. There is a corresponding relationship between the absolute humidity, saturation humidity, relative humidity and temperature of the air. If the temperature changes, all kinds of humidity also change.

Dew point: dew point refers to the air containing a certain amount of water vapor (absolute humidity). When the temperature drops to a certain degree, the water vapor contained will reach a saturated state (saturated humidity) and begin to liquefy into water. This phenomenon is called condensation. The temperature at which water vapor begins to liquefy into water is called “dew point temperature”, or “dew point” for short. If the temperature continues to fall below the dew point, the supersaturated water vapor in the air will condense into droplets on the surface of commodities or other materials. In addition, wind is closely related to the temperature and humidity in the air, and it is also one of the important factors affecting the change of air temperature and humidity.

Change of temperature and humidity inside and outside the warehouse: from the analysis of the law of temperature change, generally, the appropriate time to reduce the temperature in the warehouse in summer is from 10 o’clock at night to 6 o’clock the next morning. Of course, the influence of commodity characteristics, warehouse conditions, climate and other factors should be taken into account in cooling down.

Temperature and humidity control of storage space

Measurement of temperature and humidity of storage space: the traditional use of dry and wet bulb thermometer for measuring air temperature and humidity. The dry and wet meter shall be set outside the warehouse. In order to avoid the invasion of sunlight, rain and dust, the dry and wet meter shall be placed in the shutter box. The temperature and humidity in the warehouse must be observed and recorded regularly every day, generally from 8 a.m. to 10 a.m. and from 2 p.m. to 4 p.m. The records should be properly kept, analyzed regularly and found out the rules, so as to grasp the initiative of commodity storage. Compared with traditional methods, the new April high-precision temperature and humidity recorder has high precision, 100000 groups of large capacity data, automatically records temperature and humidity data, convenient operation, stable working performance, and is an effective temperature and humidity monitoring equipment.

Control and adjust the temperature and humidity of the storage space: in order to maintain the quality of goods in the storage space and create an environment suitable for commodity storage, when the temperature and humidity in the warehouse are suitable for commodity storage, we should try to prevent the adverse impact of the climate outside the warehouse on the warehouse; When the temperature and humidity in the warehouse are not suitable for commodity storage, effective measures should be taken in time to adjust the temperature and humidity in the warehouse. Practice has proved that the combination of sealing, ventilation and dehumidifier is an effective method to control and adjust the temperature and humidity in the warehouse.

Sealing: sealing is to close the goods as tightly as possible to reduce the impact of external adverse climatic conditions, so as to achieve the purpose of safe storage. The sealing method should be combined with ventilation and moisture absorption. If it is used properly, it can achieve many effects, such as moisture-proof, mold proof, heat proof, melting proof, dry crack proof, antifreeze, rust proof, insect proof and so on. Precautions for sealed storage: before sealing, check whether the quality, temperature and water content of the goods are normal. If mold, insects, fever, water glaze and other phenomena are found, they cannot be sealed. It is found that the moisture content of the commodity exceeds the safe range or the packaging material is too damp, and it is not suitable to seal it. The sealing time shall be determined according to the performance and climate of the commodity. Goods that are afraid of moisture, melting and mildew should be sealed in the season of low relative humidity. Common sealing materials include plastic film, moisture-proof paper, linoleum, reed mats, etc.

Ventilation: ventilation is to use the air pressure difference formed by the different air temperatures inside and outside the warehouse to make the air inside and outside the warehouse convection, so as to achieve the purpose of adjusting the temperature and humidity in the warehouse. The greater the temperature difference between inside and outside the warehouse, the faster the air flow; If there is wind outside the reservoir, the pressure of the borrowed wind can accelerate the convection of air inside and outside the reservoir. However, the wind force should not be too strong (the wind force is more than level 5, and there is more dust). Proper ventilation can not only adjust and improve the temperature and humidity in the warehouse, but also timely distribute the excess moisture of commodities and packaging. According to different purposes of ventilation, it can be divided into two kinds: cooling (or warming) by ventilation and dispersing moisture by ventilation.

Dehumidifier: in rainy seasons or rainy days, when the humidity in the warehouse is too high for commodity storage, and the humidity outside the warehouse is too high for ventilation and moisture dissipation, dehumidification can be used to reduce the humidity in the sealed warehouse. With the continuous development of market economy, mechanical moisture absorption method is widely used in the storage space of modern shopping malls. Use the hygroscopic machine to suck the wet air in the warehouse into the dehumidifier cooler through the exhaust fan, so that it condenses into water and is discharged. Dehumidifiers are generally suitable for moisture absorption and moisture dissipation between warehouses for storing cotton cloth, knitted cotton fabrics, valuable department stores, medicine, instruments, electrical equipment and cigarette sugar.

Post time: Jul-09-2022