DE4023533A1 - Cooling system for electronic systems - has direct cooling provided by circulated fluid cooling process - Google Patents

Abstract

A cooling system is used for electronic equipment and has cooling fluid circulated by a pump (1). The cooling fluid is passed through tubes that connect with elements (20a-20c). Return lines pass the fluid back to the system for reuse. The surfaces of the cooling elements are in contact with the heat generating units. They allow the temperature to be reduced without having to heat the ambient air. ADVANTAGE - Efficient cooling of electronic systems.

Description

Liquid cooling system for electronic systems

The invention relates to a cooling system for electronic systems Claim 1.

A cooling system for electronic systems is intended to prevent the operating temperature within a system does not reach a critical temperature point exceeds and ensures permanent operation of the system. It is it is important that on the one hand the temperature of the ambient air within the System is kept so low that the modules are still a cool obtained, and on the other hand, it would be desirable to control the junction temperature rature of important electronic components such. B. of power semiconductors in keep a defined area to ensure their operability most.

This has been users and manufacturers of electronic systems for a long time known, so that years ago liquid cooling systems for high-performance computing IBM, CRAY, DEC, SIEMENS were developed as normal Ventilation systems were not sufficient.

In this case, normal ventilation systems are ventilation through forced convection tion within the system by outside air, such as z. B. in high power calculator Cyclone from Tandem Computers or almost everyone conventional electronics cabinets can be used.

Now there are liquid cooling systems that result from the combination of the two stood, but only the effect of cooling the convection air by means of Use the coolant through which the heat exchanger flows (e.g. from Behr, Stuttgart).

The development of electronics to ever smaller components and the resulting ones following higher assembly options of circuit boards required today Cooling systems as they have been used in high-performance computers. These However, liquid cooling systems have due to the requirements of their Security such a complicated construction that it can only be found in expensive, specially designed computers are used, because the cooling liquid is under a certain pressure, which in the event of a leak could destroy the entire system.

However, cooling with forced convection is safer, but it is Cooling effect for such systems due to the low temperature difference unsatisfactory. This type of ventilation also causes very strong Wind noise, which is a considerable nuisance for the user and also affects operational safety due to the suctioned dust particles that gradually build up on the electronic components and affect the operation.

In many cases, a lack of knowledge of thermodynamics only makes them global Cooling measures taken.  

The object of this invention is now to develop a method wrap and create a system after finding the heat sources this cools directly, the design effort being largely minimized and gives the user the opportunity to use an effective liquid cooling system, which is used for commercially available standardized elec tronic components and component groups can be used.

In addition, the system must be absolutely leakproof and versatile be.

This object is achieved in accordance with the invention as they characterize the part of claim 1 has been described.

advantages

With the method and the plant it is achieved that a liquid cooling system for cooling commercially available standardized components and Component groups can be used.

Another advantage is the possibility of direct component cooling based on a detailed thermal analysis of the flow behavior the components of the overall system.

Another advantage is a mobile, practically unlimited space Possible application of the cooling system.

The advantage is the special cooling effect due to the heat transfer the components onto a turbulent liquid cooling medium.

The advantage is the absence of forced convection of the ambient air of the components within the system components.

The advantage is a closed system, the internal pressure to the outside pressure represents a defined negative pressure and therefore at Lekag the cooling medium cannot escape.

Another advantage is the almost unlimited possibility of Design of the cooling elements and the exact coordination the requirements.  

An embodiment of the invention is shown in the drawing and described in more detail below.

A) The supply unit (see Fig. 1)

The supply unit consists essentially of the cooling block ( 1 ) and the circulation pump ( 2 ).

The cooling block is a container for the cooling liquid ( 3 ), connected to Peltier elements ( 4 ), which regulate the cooling liquid at the desired temperature via temperature sensors. The cooling system is closed and has a negative pressure to the ambient pressure, and the amount of the cooling medium determines the size of the container and corresponds to the volume of all cooling elements. The circulation pump is designed so that it can generate a turbulent disturbance of the cooling medium Re <2320 anywhere in accordance with the pipe cross-sections. This is absolutely necessary because this is the only way to achieve the desired cooling effect. This will be discussed in more detail below.

B) The cooling elements (see Fig. 2, 5 - 7 )

The cooling elements consist of metals with high thermal conductivity. in the The most common case is aluminum, but can also be used in exceptional cases len consist of copper or precious metals.

Their design is such that the heat source (electronic component) should be a smooth, flat surface, shallow roughness, with the thinnest possible wall, the outer partial surface of a cooling channel that contains the cooling liquid (see Fig. 5). For gün stigiger heat dissipation, the opposite outer surface is formed with cooling fins. The required volume is determined by the heat transfer surface, the surface temperature of the heat source and the permissible temperature difference with turbulent flow still present. Due to the cooling fins, the surface of the cooling elements must be designed so that no condensation occurs due to the temperature difference.

C) The control unit (see Fig. 3)

The control unit essentially consists of the electrical control and regulating unit ( 8 ) and the level control ( 9 ). After switching on, the control and regulating unit supplies the system with energy and monitors all electrical and thermal functions of the system. The level control includes a vacuum pump ( 10 ) and a level control valve ( 11 ), by means of which the internal pressure of the cooling system and the cooling water level are constantly monitored and, if necessary, regulated.

function

Fig. 4 shows the functional diagram of the principle described. The cooling block consists of the container 1 and the cooling unit 12 . Container 1 is connected via the riser 14 directly to the level controller 13 . After filling the container in the cooling block with the coolant, the vacuum pump built into the level controller is switched on. It creates a negative pressure in the system, and consequently atmospheric pressure presses coolant into the cooling system through the opening 15 . When the coolant reaches a certain level, the circulation pump 2 is automatically switched on and the vacuum pump switched off. Via the feed line 16 and the connecting lines 17 a- 17 c, the coolant now passes into the cooling elements 20 a- 20 c. After it has flowed through the cooling elements, it is redirected via the connecting lines 18 a- 18 c and the discharge line 21 into the container. The slide 19 a- 19 c the NEN to shut off and secure the system.

In the container, the coolant is brought to the specified temperature cooled down.

The cooling effect Direct component cooling

The cooling effect created according to this principle is to be illustrated on a diagram ( Fig. 5).

Because in this case the heat source and cooling element are directly connected to each other are connected from a heat transfer through heat conduction the contact area: Formula 1:

The heat exchange between the wall of the cooling channel and the moving The coolant can then be described as follows: Formula 2:

_Z = α × A × (T _F - T _W )

One can rightly assume that on the wall of the Cooling channel almost the temperature of the Component. Thus

T₁ ≈ T₂ == <Δ T ≈ 0

and the heat transfer through heat conduction is negligible small, and you can only calculate according to Formula 2.  

This formula also applies to the cooling process, only are swapping the temperatures: Formula 3:

_Z = α × A × (T _W - T _F )

This includes the heat transfer coefficient in W / m²K all influences of the properties and the movement exchange of the Liquid and the wall (e.g. roughness).

The order of magnitude of the heat transfer coefficient when forced The flow for water is between 580 and 11,650 W / m²K.

The total amount of heat to be dissipated can be obtained by adding the construction partial heat quantity can be determined:

_ZGES = Q _Z1 +. . . + Q _Zn

Cooling through heat exchange

At locations within the electronics cabinet that are not directly ge are cooled, heat is exchanged through radiation. Spe purpose-built cooling elements with core temperatures up to Can be 200 ° K below the surface temperature of the components, extract the heat from the ambient temperature. In these cases be the heat exchange is calculated as follows:

C _{S is} the radiation constant of the absolutely black body with 5.77 W / m² (K) ⁴. However, since there are absolutely no black bodies in nature, the radiation coefficient of the real body C is always smaller than C _S.

The heat absorption by the heat sink can then be done like describe as follows:

If the warmer body (T₁) with the surface A₁ of that colder body (T₂) completely enclosed with the surface A₂, so is

By breaking it down into smaller cooling zones, the individual items can be invoices at key points the desired total cooling station stung be achieved.

Claims (12)

Liquid cooling system, consisting of supply unit, cooling elements and control unit for cooling commercially available, standardized elec electronic components and assemblies in electronic cabinets with variable cooling elements and direct component cooling through forced convection (tur bulent flow) of the liquid cooling medium by means of exact thermal Analysis of the flow behavior of air in the electronics cabinet. The process and the system are characterized by the following features: 1. Before designing the cooling system, a thermal analysis of the flow behaved within the plant. 2. The system is characterized by the direct placement of the cooling element elements on the heat-developing components. 3. The process is characterized by the heat transfer from the building component flow onto a fluid, turbulent flowing medium. 4. The procedure is characterized by the arithmetic breakdown into individual cooling zones with the same ambient temperature. 5. The system is characterized by cooling without forced air circulation out. 6. The system is characterized by its built-in cooling system that makes it independent of heat exchangers and cooling water pipes. 7. The system is characterized by a closed vacuum system which does not result in any coolant leakage in the event of leakage. 8. The system is characterized in that the use of gases as a cooling medium is possible without restriction. 9. The system is characterized by specially developed and precise calculated cooling elements, the heat exchange by convection and Enable radiation. 10. The system is characterized by the construction of the components, which are matched to the worldwide standard 19-inch system.