JP2005055158A - Method for supplying cold insulating agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply a large quantity of a cold insulating agent suitable for food refrigeration in a day cycle. <P>SOLUTION: The internal temperature of a refrigerator comprising a compressor of 1,000 W or more is set to -40°C or lower, and the cold insulating agent having a freezing retention temperature of -25°C or lower is put therein with clearances. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

Detailed Description of the Invention

Industrial application fields

  The present invention relates to a system for efficiently supplying a cryogen.

  In a general freezer that freezes a conventional cryogen, it is not practical because it takes a long time to freeze a large amount of a low temperature cryogen suitable for food freezing (−20 ° C. or lower). Therefore, dry ice is generally used.

Problems to be solved by the invention

  Provided is a method for efficiently supplying a cryogen so that the inside temperature when the cryogen is added becomes a low temperature suitable for food freezing.

Means for solving the problem

  First, a quick freezer is prepared, in which a gap is opened and a cryogen is filled, taken out after freezing, and then another cryogen is opened in a gap and placed in the quick freezer to be frozen. In the present invention, it is a quick freezer that uses a compressor of 1000 W or more to obtain an internal temperature of −40 ° C. or lower, and the cryogen must be −25 ° C. or lower. According to this system, while it is taken out after freezing and used for cold storage, a new frozen cryogen can be used immediately when the previous cryogen is exhausted by freezing another cryogen. Can occur. This is hereinafter referred to as a circulation cycle.

  In addition, in order to quickly freeze the number of cryogens having the full refrigeration capacity, it is difficult to keep the cryogens in close contact with each other, and it is necessary to freeze them with a gap. There are two ways to provide a gap. One is to create a space between the cold insulation and the other so that the cold insulation is not in close contact with the partition, and the other is This is a way to make the shape of the container of the cryogen into a curve and to create a natural gap when overlapped.

  The reason why it is essential to have a gap in a freezer of 1000 W or more is based on the following experiment. That is, if a freezer of 1000 W or more (with an internal volume of 100 L) and an internal temperature of about −45 ° C. is used, 100 pieces of 550 ml of −36 ° C. refrigeration agent for −36 ° C., that is, 55 L can be frozen in 20 hours. It was. Moreover, if a freezer with an internal volume of 400 L was used, 110 L could be frozen within 24 hours. In this way, a large amount of the cryogen can be supplied in a daily cycle.

  In the present invention, there are the following two reasons for using a cryogen at -25 ° C or lower. The colder the colder, the longer it takes to freeze, and using a freezer with a normal cold insulation capacity would require several days to freeze a lot of the cryogen at a time. The circulation cycle cannot be obtained. That is, the need for a quick freezer is limited to low temperature cryogens. Next, in order to keep -20 degrees C or less required for food freezing, as can be seen from Reference Example 1, a refrigeration agent of -25 degrees C or higher is necessary.

  Examples of the cryogen having a melting point of −25 ° C. or lower include those having a melting point of −25 ° C. or lower, eutectic one having −25 ° C. or lower and another melting peak near −20 ° C., and a main melting point of, for example, −30 There are three types, such as those that are ℃ but then gradually increase in temperature, but that do not rise above -25 ℃ for a long time. Many belong to the third.

  Specifically, (i) calcium chloride aqueous solution (-55 ° C), (ii) magnesium chloride aqueous solution (-31 ° C), (iii) mixed aqueous solution of magnesium chloride and calcium chloride (-37 to -45 ° C), etc. There is. However, since these differ in temperature depending on the concentration, they indicate the lowest temperature that can be reached.

  The above (i) to (iii) are compared with a well-known -15 to -20 ° C cooling agent such as an aqueous ammonium chloride solution (-15 ° C), an aqueous ammonium nitrate solution (-18 ° C), and an aqueous sodium nitrate solution. Retention time is short. That is, there is a drawback that the latent heat is small. Therefore, among combinations of (i) to (iii) and a cryogen having a long holding time of −15 to −20 ° C., a combination having an average temperature of −25 ° C. or lower is used, and −20 ° C. or lower. Can be maintained for a long time. Specifically, there is a combination of (i), (ii) or (iii) and an aqueous ammonium chloride solution (−15 ° C.), or a combination of ammonium nitrate (−18 ° C.). In the combination of −30 ° C. and −18 ° C., −30 ° C. and 1/2 and −18 ° C. may be halved, but in the combination of −30 ° C. and −15 ° C., −30 ° C. 2/3 amount, −15 ° C. is defined as 1/3 amount.

  In a general freezer, it takes a long time to freeze the cryogen. In addition, if the container is too thick, the amount of heat transfer is reduced, and freezing requires a longer time. Therefore, the thickness of the container of the cryogen is generally about 1.5 mm when it is made of polyethylene, and is at most 2 mm. By increasing the thickness, the holding time of the cold-retaining effect can be lengthened, but further time is required for hydration. This problem can be solved by a quick freezer, increasing the thickness, lasting for a long time, and freezing quickly. If the thickness of the container is 3 mm, the holding time is 1.2 to 1.5 times longer in the case of 2 mm, and 2.5 to 3 times longer than in the case of 1 mm. However, if it is too thick, it will take a long time to freeze even if quick freezing is used. Also, the weight of the container increases. Therefore, in the present invention, a polyethylene container having a thickness of 2 to 5 mm is most preferable.

  The thermal conductivity of PET bottle polyester is about 1/3 that of polyethylene. Therefore, if a polyester container is used, 1 mm in thickness corresponds to 3 mm in polyethylene. Therefore, if the polyester container is thin and light with a thickness of 0.7 to 1.6 mm, the holding time can be extended.

  Embodiments of the present invention are shown below. A quick freezer having a freezing capacity of preferably 1 to 2 kW / h and an internal volume of preferably 200 to 1000 L is composed of a magnesium chloride aqueous solution, a magnesium chloride and calcium chloride mixed aqueous solution, an ammonium chloride and sodium nitrate mixed aqueous solution, or a calcium chloride aqueous solution. 100 to 300 refrigerants are placed and placed in such a manner that a partition is provided so that a gap thickness of at least about 10 mm can be formed in both the upper, lower, left and right sides, and the freezing agent is completely frozen. After confirming freezing, take it out and freeze it with another cryogen. This additional refrigeration agent is preferably pre-cooled in a refrigerator before being added. Polyethylene is used as a container for the cryogen. The thickness may be a general one of 1 to 2 mm, and if it is desired to increase the holding time, a thickness of about 2 to 5 mm is used. When using the thing made from polyester for the purpose of lengthening holding time, the thing of about 0.7-1.6 mm is used.

Reference example 1

  A polyethylene container 19.5 × 13.5 × 2.5 cm (polyethylene thickness 1.5 mm) filled with 550 ml (600 g) of a −37 ° C. cryogen (magnesium chloride 20%, calcium chloride 5%). About 120 kg was packed in the upper cooling agent installation part of the air container, the temperature change with time in the lower part of the cabinet was measured, and the results are shown in Table 1. The outside temperature was 21 ± 2 ° C. For comparison, 120 kg of a conventional product (manufactured by Yamato Transport Co., Ltd.) was also measured. The cooling agent of the calcium chloride / magnesium chloride mixed liquid was kept at −30 ° C. or lower for 18 hours and −20 ° C. or lower for 25 hours. The conventional product at -21 ° C could only hold for 3 hours at -20 ° C or lower. As a result of additional experiments, it was found that in order to maintain the -20 ° C. necessary for food freezing for a long time, it was not suitable for a cryogen having a melting point of -21 ° C. and had to be −25 ° C. or lower.

  In a quick freezer with a refrigeration capacity of 1 kW / h (internal temperature −42 to 45 ° C.), the cryogen for −37 ° C. (one size 19.5 cm × 13) left in a 30 ° C. room of Reference Example 1 (0.5 cm × 2.5 cm) 90 pieces were packed and packed so that the gap was 10 mm in both the top, bottom, left and right. Separately, 90 pieces were packed in a 200 W general freezer in the same manner. The time required for all the cryogens to freeze was 20 hours in a quick freezer. Since 90 pieces can hold | maintain the internal temperature to -20 degrees C or less for about 1 day, it turns out that the cooling agent supply cycle of a 1-day cycle is possible. On the other hand, in the case of a general freezer, the internal temperature became only −25 ° C. in 20 hours and did not freeze.

Claims (3)

  A cryogenic agent supply method characterized in that, in a quick freezer using a compressor of 1000 W or more, the inside temperature is set to −40 ° C. or lower, and a cryogen having a holding temperature at freezing of −25 ° C. or lower is inserted with a gap. .   The method for supplying a cooling agent according to claim 1, wherein the cooling agent is a combination of those having a temperature of -28 ° C or lower and those having a temperature of -15 ° C or lower.   The method of supplying a cooling agent according to claim 1 or 2, wherein the container of the cooling agent is made of polyester having a thickness of 0.7 to 1.6 mm, or made of polyethylene having a thickness of 2 to 5 mm.