EP1225402A1

EP1225402A1 - Refrigeration installation with reduced hysterisis

Info

Publication number: EP1225402A1
Application number: EP01120838A
Authority: EP
Inventors: Fausto Tacconi
Original assignee: Fausto Tacconi
Current assignee: EDILCOLOR - SOCIEDADE DE COSTRUEOES LDA
Priority date: 2001-01-18
Filing date: 2001-08-30
Publication date: 2002-07-24
Also published as: PT102551A

Abstract

The refrigeration installation with reduced hysterisis consists of a refrigerating fluid compressor (1), a codenser (2), a lamination valve (8) and an evaporator (10,22) for exchanging heat with the refrigerated fluid; it has an injection line (3) of hot gases taken downstream of the compressor (1) and injected upstream of the evaporator (10); it has at least one injection command and control electrovalve (9); it also has a second interception electrovalve (7) placed upstream of the lamination valve (8); this second electrovalve (7) is activated in phase inversion in relation to injection command and control electrovalve (9); it also has a probe (21,26) for indicating the temperature of the refrigerated fluid at the exit of the evaporator (10,22), the probe being situated in proximity thereto.

Description

The invention relates to a refrigeration installation with reduced hysterisis, i.e. an installation for refrigerating liquid or gaseous fluids which, owing to its special constitution, makes it possible to extract large amounts of heat in the presence of very low oscillations in the temperature of the fluid itself; it is appropriate for cooling high technology machinery such as laser beam apparatus, linear motors, etc., and can clearly be used for a very wide range of functions.
Prior art includes various type of installations for cooling technological fluids used in the functioning of machines or their components, in which a refrigeration installation consist at least of a hermetic compressor, a condenser, a dehydrating filter, a lamination valve an evaporator and a liquid separator, with thermostatic electrovalves for switching the respective compressor on and off, according to the amount of gas to be compressed, through the evaporation thereof in the aforementioned evaporator.
Furthermore, a similar installation has considerable technological limits even when various types of pressostats are used, namely at the time of intervention, and it is obviously affected when the compressor is switched on and off as it is unable to reduce below a certain limit the technical time for switching the actual compressor on/off. In order to prevent this situation, prior art uses thermostatic laminations valves or automatic connection pressostats but it has only been possible to reduce the hysterisis of the on/off cycle of the compressor by a few degrees Celsius.
Furthermore, in order to avoid oscillations in the temperature of the refrigerated liquid, the use of tanks or containers with a large capacity for storing liquid is well known in prior art, in order to distribute over a larger mass the oscillations of extracted heat required by the machines, thus obtaining a slower oscillation in the temperature of the machine or of the cooled component.
Likewise, an identical increase in the mass of the refrigerated liquid leads to a much slower oscillation even when the temperature is close to the permitted limits and the refrigeration installation must intervene to extract heat: the inertia presented by the large mass of fluid therefore becomes an undesirable inertia for the refrigeration action because it slow down its effects an consequently slows down the increase in the temperature of the liquid.
In modern technology, machines which use lasers, linear motors, electronic mandrels, electroerosion, etc. require the lowest possible temperature oscillation of their cooling fluid in order to function more efficiently: ideally, it should remain constant in order to ensure a more efficient functioning.
Considerable improvements could be made to prior art in order to drastically reduce the aforementioned hysterisis in the functioning of the refrigeration installations.
In view of the above, there is a need to resolve the technical problem by devising a configuration for the refrigeration installation which permits a considerable reduction in the constant of the intervention time of the temperature control of the refrigerated/refrigerating fluid; furthermore, this configuration should make it possible to reduce the mass of the refrigerated/refrigerating fluid.
The invention resolves the technical problem described above, by adopting a refrigeration installation with reduced hysterisis, which consists of a condenser, a lamination valve and an evaporator for exchanging heat whit the refrigerated fluid, characterised for this purpose in that it has an injection line of hot gases taken downstream of the compressor and injected upstream of the evaporator; it has at least one injection command and control electrovalve.
By adopting, in a preferred embodiment in combination with the aforementioned electrovalve, a second interception electrovalve placed upstream of the lamination valve; this second electrovalve is activated in opposite phase in relation to the injection command and control electrovalve.
By adopting, in a successive and preferred embodiment, a probe for indicating the temperature of the refrigerated fluid situated at the exit of the evaporator and in proximity thereto.
By adopting, in a successive and preferred embodiment, a plate type evaporator, with the probe for indicating the temperature of the refrigerated fluid placed immediately downstream thereof.
By adopting, in a successive and preferred embodiment, an evaporator of the type immersed in the tank of refrigerated liquid whit the probe for indicating the temperature of the refrigerated fluid placed inside the coil of said evaporator.
By adopting, in a successive and preferred embodiment, a plate evaporator connected cocurrently to the movement of the refrigerating/refrigerated fluids.
The advantages gained with this invention are the following: the functioning of the installation presents a hysterisis which can be reduced to a few tenths of a degree, thus reducing the mass of the refrigerated fluid in relation to the cases observed in prior art; the injection of gaseous fluid heated downstream of the evaporator sharply influences the heat extracted therefrom by the refrigerated fluid: the reduced mass of the refrigerated fluid present in the evaporator permits a rapid adaptation and control of the aforementioned injection. The refrigerating compressor can therefore function under the best conditions possible with a considerable increase in its useful life; in fact, the number of on/off cycles of compressors is limited, but with the installation described herein the compressor can function constantly under the ideal conditions intended at the time of manufacture.
An embodiment of the invention is illustrated simply by way of example in three drawings attached hereto, in which Figure 1 represents a diagram of the refrigeration installation according to the invention; Figure 2 represents a diagram showing its application in a machine in operation, whereby the refrigerated fluid is directed to said machine after transferring the heat to the evaporator of the refrigeration installation, with the evaporator immersed in the tank of refrigerated fluid; Figure 3 represents a diagram of the application shown in the preceding Figure, but with the plate evaporator connected in continuous current to the refrigerating and refrigerated fluid circuits.
The following are indicated: as 1, Figure 1, the hermetic compressor, which feeds the compressed refrigerating fluid to the condenser 2 and an injection line 3; as 4, the dehydrating filter and, as 5 and 6, the maximum and minimum pressostats; as 7, an electrovalve to control the feeding of the lamination valve 8 of the refrigerating liquid; as 9, an electrovalve to control the compressed gaseous fluid coming from the injection line 3; as 10, the evaporator in contact with the refrigerated fluid, whose circuit is represented in Figure 2; as 11, a liquid separator and as 12, a pressostat for controlling the functioning of the aforementioned hermetic compressor 1; as 13, Figure 2, a tank for the refrigerated fluid, inside which the aforementioned evaporator 10 is placed; as 14, a pump for sending the refrigerated fluid to the machine components 15/a, 15/b and 15/c; as 16, a filter in the sending of the fluid and as 17, the return of the fluid in the tank 13 of the machine; as 18, a probe for indicating the temperature for sending the refrigerated fluid; as 19/a, 19/b and 19/c, the hot areas of the components of the machine from where the tube 20 leaves for returning the refrigerating fluid to the aforementioned tank 13, which extract the heat dispersed during functioning; as 21, the probe for indicating the temperature of the fluid situated inside the coil of the evaporator 10; as 22, Figure 3, an evaporator connected in continuous current between the refrigerating/refrigerated fluids, the latter coming from tube 20 and exiting in tube 23, in the direction of the tank 24; as 25 and 26, two probes indicating the heat variation, between the upstream 25 and downstream 26 of the evaporator 22, in the refrigerated fluid.
The functioning of the installation according to the invention is as follows. The fluid which is refrigerated and condensed in the condenser 2 reaches the lamination valve 8, but downstream of said valve it receives the injection of the compressor fluid, taken upstream of the condenser through the tube 3, controlled by the electrovalve 9 which opens as an alternative to the electrovalve 7; the exchange of heat between the refrigerating fluid and the refrigerated fluid takes place in the evaporator 10 or 22 in a controlled manner, with the probe for indicating the temperature of the refrigerated fluid 21 or 25 and 26, which controls the selection of the opening of the electrovalve 9 and therefore of the injection or of the electrovalve 7 and therefore of normal functioning; the difference in relation to the ideal temperature for the functioning of the apparatus 15/19 is indicated in due time, i.e. at the closest point of the exchange zone between the two refrigerating/refrigerated fluids and, always for the reduced mass of the refrigerated fluid present between the probes 21 or 25 and 26, the speed of the control intervention on the aforementioned electrovalve 9 for opening/closing the injections in the tube 3 makes it possible to achieve very low intervention times and therefore very low differences in relation to the ideal temperature.
The mass of the refrigerated fluid in the embodiment with the plate evaporator of Figure 3 compressed between the two probes 25 and 26 is reduced and the effect of the injection of the refrigerated fluid heated upstream of the evaporator also causes the temperature of the refrigerated fluid to rapidly increase, which is indicated downstream of said evaporator by the probe 26: once the stipulated value has been reached the probe activates the aforementioned electrovalves, 7 at the opening and 9 at the closure, returning to normal functioning.
What has been stated above allows the refrigerated fluid in the tank 22 to maintain a constant temperature and the refrigerating liquid pumped by the pump 14 presents a very slight heat increase visible to the user through the probe 18.
Finally, the refrigeration installation equipped with the evaporator 10 immersed in the tank 13 has a similar functioning if the probe 21 for indicating the temperature of the refrigerated fluid is placed inside the coil of said evaporator; the mass of the refrigerating fluid in this case is greater than the installation of Figure 3, but the injection of the heated fluid and the increase in temperature with the probe 21 also make it possible to obtain notable improvements in the reduction of the thermal hysterisis of the refrigerated fluid.
In practice, the materials, dimensions and certain details may be different from the ones indicated herein, but they are technically equivalent and therefore do not go beyond the legal scope of this invention.

Claims

A refrigeration installation with reduced hysterisis, characterised in that it consists of a refrigerating fluid compressor (1), a condenser (2), a lamination valve (8) and an evaporator (10, 22) for exchanging heat with the refrigerated fluid, whit an injection line (3) of hot gases taken downstream of the compressor and injected upstream of the evaporator, and also at least one injection command and control electrovalve (9).
A refrigeration installation according to the preceding claim, characterised in that it has in combination with the aforementioned electrovalve (9) a second interception electrovalve (7) placed upstream of the lamination valve (8), this second electrovalve (7) being activated in phase inversion in relation to the injection command and control electrovalve (9).
A refrigeration installation according to one of the preceding claims, characterised in that it has a probe (21, 26) for indicating the temperature of the fluid at the exit of the evaporator (10, 22), situated in proximity thereto.
A refrigeration installation according to one of the preceding claims, characterised in that it has a plate type evaporator (22) where the temperature indicating probe (26) is placed immediately downstream thereof.
A refrigeration installation according to one of the preceding claims 1 to 3, characterised in that it has an evaporator (10) of the type immersed in the tank (13) of refrigerated liquid, with the probe (21) for indicating the temperature of the refrigerated fluid placed inside the coil of said evaporator (10).
A refrigeration installation according to the preceding claim 4, characterised in that it has a plate evaporator (22) connected cocurrently to the flow of the refrigerating/refrigerated fluids.