DE1903585A1 - Test chamber with cooling system - Google Patents

Description

Dipl.-Ing. W. PAAP: 8 MONKS 22, DIpI-In ,. H. MITSCHERUCH Dipl..Ing. K. GUNSCHMANN "" ⁸⁴ Dr. r * r. not. W. KÖRBER ² ^ · ^Jan · ¹⁹⁶⁹ PATENTANWÄLTE / Bra.

ASSOCIATED TESTING LABORATORIES, INC.
200 route H 6

Wavne. New Jersey O7H7O / V.St.A. Patent application

Test chamber with cooling system -

The invention relates to test chambers and, more particularly, to a test chamber for low temperatures', which · in combination with an improved Cooling system is designed using mixed halogenated hydrocarbons as a coolant.

Test chambers with conventional refrigeration systems using a single compressor and a single refrigerant liquid have heretofore generally operated with temperatures in the range of - ^ 0 ° C (- k0 ° F) as the effective lower limit. Lower temperatures are generally obtained with the aid of more complicated and expensive cooling systems of the double or cascade type, with one or more separate coolants and a duality of

components are used. Mixed coolants are also available for such use has been suggested, however, in such cases the proposed use has resulted in relatively complex and costly devices that have no competitive advantage and are economically unsuitable for use as small or medium-sized test chambers

909835/1071

j The invention is intended briefly as an improved construction of a Prüfj chamber are described, which consists of a refrigeration system that has a single compressor and evaporator in conjunction with a contains mixed halogenated hydrocarbons as a coolant.

Among the advantages that can be achieved with the test chamber according to the invention The rapid achievement of temperatures of -65 C is one of the key elements (- 85 F) in a simple and inexpensive unit consisting of common and readily available components and consequently from an inexpensive test chamber with a remarkable wide testing area.

The subject of the invention is an improved test chamber which contains cooling systems using a mixed halogenated hydrocarbon as a coolant and which is intended to serve in particular for the use of low temperatures.

With reference to the drawing, the inventive The object and the advantages that can be achieved with it are described in more detail: _. -

1 shows a side view, partially cut away, of the test chamber according to the invention,

FIG. 2 is a schematic diagram of the in the unit of FIG ■ Fig. 1 contained cooling system. /

> ■■ · ■ ■■■ ■■ ■ - ■■ -

The test space 10 according to FIG. 1 is relatively small and can be placed on a table. It consists of a temperature control part 12 and a part, the chamber section 14 records. A chamber space 16 is centrally located in chamber section IU arranged, which is surrounded by insulated walls of suitable thickness and accessible through an insulated door 18. In the control part 12 suitable elements for heat generation, means for air circulation, controls, and components for cooling are arranged. At the front of temperature control part 12 are Easily accessible control and display of the work process

j elements 20 provided · A display thermometer 22 is attached to the Door 18 attached.

BAD ORiQINAL

As already mentioned, test chambers previously had the one described above Type because of their size and in terms of cost factors a low temperature working limit of - 40 ° C when using the usual Refrigeration.

The test chamber according to the invention has an improved cooling system that effectively reduces the working temperature to below -65 ° C (-85 ° F) lowers. The cooling system uses mixed halocarbon refrigerants of certain types, as further described below will. The operative components of the system are indicated in FIG.

A first component of the halogenated hydrocarbon coolant mixture according to the invention is selected from the group of dichlorodifluoromethane (R 12), tf44 monochlorodifluoromethane (R 22) and an azeotropic mixture (R 502) of monochlorodifluoromethane (R 22) and monochloropentafluoroethane (R 115) second component! from the group of monochlorotrifluoromethane (R 13). All such coolants are commercially available, including from EI du Pont de Nemours ε Co. and Allied Chemical Corporation. The preferred first ingredient consists at least in part of dichlorodifluoromethane (R 12) because of its miscibility with oil. The azeotropic mixture R 502 consists of 48.8 percent by weight monochlorodifluoromethane and 51.2% monochloropentafluoroethane. It is available from EI du Pont de Nemours S Co. as Freon 502, among others. According to the manufacturers, the substances R 502 ^have: R 12 and R 22 the following features:

909835/1071

- 4 - (R ₂₂ ) 190358! ^(R 5O2 ^} Freon 22 (R ₅₂ ) Freon 502 CH Cl F ₂ Freon 12 Chem. Formula x) 86.48 C Cl ₂ F ₂ Mole weight 111.64 xx) -41.4 ° 120.93 Boiling point (F °) -50.1 ° -40.8 ° -21.6 ° Boiling point (C °) -45.6 ° -29.7 ° Damp f pressure (ps i a) 277.3 at 48.9 ° C 295 38.8 172.4 at -17.8 ° C 45.9 23.8

Compression ratio, 120% °

Density, liquid (g / ccm) at 48.9 ° C at -17.8 ° C

Dfchte, saturated water vapor lbs / cu.ft. at -17.8 ° C

Spec · heat ratio Cp / Cv

65 ° F and 10 psia

Latent heat of vaporization
Btu / lb 0 ° F

6.43

1,121 1,395

1.104

7.15

1,089
1,345

0.728

1,132

1,187

Solubility of water (ppm)

25.5 ° C

69.61

560

94.39

1300

7.24

1,216 1,449

0.622

1,139

68.75

93

χ) CH Cl F ₂ / C Cl F ₂ CF ₃ (48.8 / 51.2 percent by weight) xx) Approximate value

The preferred second component consists of the azeotropic mixture (R503) which is composed of 40.1 percent by weight of trifluoromethane (R ₂₃ ) and 59.9% of monochlorotrifluoromethane (R ₁₃ ). It is received as "Genetron 23/13" from Allied Chemical Corporation- - - 5 -

07-1

borrowed. According to the manufacturer, these substances have the following properties:

Azeotrope. mixture x) Genetron 13 Genetron 23/13 87.5 ^(R 13 ^{) (R} 503 ⁾ (-127.6 ° F) -88.67 ° C C Cl F ₃ (67.1 ° F) 104.5- 19.4 ° C (-114.6 ° F) -81.40 ° C (83.9 ° F) 28.8 ° C

Chem. Formula

Mole weight
Boiling point at 1 atm.

Critical temperature

Critical Pressure (PSIA) 607 561

Heat of evaporation

Boiling point (BTU / lb) 74.2 63.9

Density, fl., At -30 ° F

(BTU / lb. ° F) 0.29 0.24

x) 40.1 percent by weight Genetron 23
59.9 percent by weight Genetron 13

To start up a device of the type described, the system is first charged with the first component of the coolant mixture, especially R ^ ο »at room temperature and a pressure of 45 psig, then at 95 psig with the second component, especially the azeotropic mixture R ₅₀₃ · Das System - is then started and adjusted so that it achieves optimal values. While the amounts of coolant used are at least partly determined by the volume of the system, about 196 g of R ₁₂ coolant and 133 g of the azeotropic mixture R _Kn o are required to achieve the desired temperature drop using the device described above, with a temperature of - 67.8 ° C (-90 ° F) can be reached in about 1 hour. On the basis of what is now achievable. limited values, it can be seen that suitable quantities of the first and second constituents

90 ^^ 571071 -

partly of coolant at least to a certain extent ■ by a weight ratio, i.e.

Weight of the first component Weight of the second component

are determinable.

In the present case the ratio is I, f7, Es has showed that deviations from the values given above lead to a decrease in the results. However, also with one Deviation by 5% temperatures in the range of -65 ° C (-85 ° F) achievable.

According to FIG. 2, the test chamber contains a compressor 30 of conventional design in order to increase the pressure of the mixed refrigerant introduced via line 28 in the gas phase. The discharge from compressor 30 is passed at high pressure via line 32 into a condenser 34 of conventional design, in which the first refrigerant component of the refrigerant mixture is selectively liquefied. The mixed gaseous-liquid coolant flowing out of the condenser is directed to a separator 36, which can expediently be in the form of a small chamber or a T-piece. The uncondensed gaseous second component of the coolant? ^e wir8 ^{hs passed} through line 30 to cascade capacitor 10. The condensed coolant is expanded by a capillary tube 44 and passed through the cascade condenser 40 in countercurrent to the second component. In this way there is an exchange of heat between the constituents and a noticeable lowering of the temperature of the second constituent of the coolant mixture. In the case of the designated coolants, such a heat exchange is sufficient to bring about condensation of most, if not all, of the second component. The liquid formed runs out of the condenser 4Q in line 4 2. The liquefied component of the second component is then expanded through the capillary tube 46 and passed to the evaporator 48, in which it absorbs heat from the surrounding parts of the device in the usual manner. The first

9 0 9 8 35V "1 β" 7 ~ 1 ~

Part of the coolant mixture leaves the condenser 40 in gaseous form via line 50 and becomes KompreaBor 30 together with the gaseous second component flowing out of the evaporator H8 via line 52, returned.

The use of dichlorodifluorine than (R ₁₂ ) ^{as the} first coolant component in connection with the azeotropic mixture (R ₅₀₃ ) of trifluoromethane and monochlorotrifluoromethane is particularly advantageous and preferred, although other combinations of the above-mentioned compounds for the first and second components of the coolant mixture are also used can be used.

As can be seen, the subject matter of the invention is only a standard device used with no valves or other maintenance disruptive components, as well as refrigerant more common and acceptable in nature. Units of the type described successfully bring the low temperature range of in accordance with the present invention small test chambers from -40 ° C (-40 ° F) to below -65 ° C (-85 ° F) without increasing component difficulty or cost.

Expectations;

Claims (9)

Expectations 1. Test chamber in combination with a cooling system, characterized in that that the test chamber one. Comprises a compressor for increasing the pressure of a gaseous refrigerant mixture, that consists of a first component from the group consisting of methane, monochlorodifluoromethane and an azeotropic mixture of monochlorodifluoromethane and monochloropentafluoroethane and a second component from the group consisting of monochlorotrifluoromethane and an azeotropic mixture of trifluoromethane and monochlorotri Fluorme than consists of a condenser for the selective condensation of the first constituent of the refrigerant mixture comprises that means are arranged on the discharge side of the condenser for separating the first and second components de "r coolant mixture, still marked by means for selectively condensing the second component by countercurrent evaporation of the first component in heat exchange with one another, as well as by means for selective evaporation of the second component of the coolant mixture 2. test chamber in combination with a cooling system according to claim 1, characterized in that the gaseous coolant mixture of dichlorodifluoromethane ale first component and one azeotropic mixture of trifluoromethane and monochlorotrifluorme than is the second component. 3. test chamber in combination with a cooling system according to claim 1, characterized in that the areotropic mixture of the first constituent consists of 18.8 percent by weight monochlorodifluoromethane and 51.2% monochloropentafluoroethane. 1. Test chamber in combination with a cooling system according to claim and 2, characterized in that the azeotropic mixture of the second component of 10.1 percent by weight tri fluotine than and 59.9% consists of mohochlorotrifluoraethine. 5. cooling system for use for the combination according to claim 1, characterized by the use of a coolant mixture consisting of a first component from the group consisting of dichlorodifluoromethane, Monochlorodifluoromethane and an azeotropic one Mixture of monochlorodifluoromethane and monochloropentafluoroethane, and a second component from the Group monochlorotrifluoromethane and an azeotropic mixture of trifluoromethane and monochlorotrifluoromethane. 6. Cooling system according to claim 5, characterized in that the first constituent from an azeotropic mixture of 48.8 percent by weight Consists of monochlorodifluoromethane and 51.2% monochloropentafluoroethane. 7. Cooling system according to claim 5, characterized in that the second component consists of an azeotropic mixture of 40.1 percent by weight Trifluoromethane and 59.9% monochlorotrifluoromethane. 8. Cooling system according to claim 5, characterized in that the coolant mixture of dichlorodifluoromethane as the first component and an azeotropic mixture of trifluoromethane and monochlorotrifluoromethane as the second component. · 9. Cooling system according to claim 8, characterized in that the azeotropic mixture of 40.1 percent by weight trifluoromethane and 59.9 weight percent monochlorotrifluoromethane. The patent attorney -fr 0 * «fr / - Blank page