Liquid cooling cold plate

Eig. 11. Liquid-cooled cold plates or heat sinks have been developed as thermal management solutions to cool components for Hquid-cooled computer systems and other electronic systems where heat removal becomes one of the important design criteria. 

Liquid-cooled cold plates perform a function analogous to that of air-cooled heat sinks. Unlike heat pipes, they may be considered active devices in that the liquid is usually forced through them by a pump. 

Indirect liquid cooling (cold plate) More efficient than thermal conduction Require pump to overcome overall pressure drop in the loop Require low thermal resistance packaging at component level... 

The pump, shown in Figs. 1 and 2, is made up of four basic components (1) one dense helium-cooled cold plate (2) two interconnected, liquid-nitrogen-cooled chevron panels (3) one gas thermometer for display of helium panel discharge gas temperature and (4) one feedthrough plate, an external bulkhead, providing connections to the helium and liquid nitrogen circuits as well as to the gas thermometer. 

The steady-state heat gain of the helium-cooled cold plate has been determined as approximately 0.1 w. This represents a net steady-state consumption of 0.25 liters of liquid helium per hour. The cool-down of the cold plate between 78° and 20 °K has been calculated to consume approximately 5 liters of liquid helium. 

The rate of condensation on a vertical surface is controlled by the force of gravity acting on the condensed liquid film. A consideration of Eq. (11.20) shows for example that for a vertical plate the mean heat transfer rate from the plate with laminar flow in the film is proportional to gw. Attempts have therefore been made to increase condensation rates by using centrifugal forces instead of the gravitational force to drain the condensed liquid film from the cold surface [55], The simplest example of this would be condensation on the upper surface of a cooled circular plate rotating in a horizontal plane. This situation is shown in Fig. 11.23. A Nusselt-type analysis of this situation will be considered in the present section. 

The MHQ apparatus is built entirely in a low-pressure chamber to preveut jet break up of tiny free jets. The low ambient pressure, the high jet velocities, and the relatively short distance to the cryo-medium result in (adiabatic) cooling of the jet. It was determined that even though the reactants are initially at ambient (20-22 °C) temperature the effective reaction temperature was 10 2°C for the cold plate setup aud 8 0.5 °C for quenching in liquid isopentane. ... 

Heat sinks are commonly attached to the surface of the spreader to provide additional surface area for heat removal by convection. The convection may be natural air convection or forced air convection via a fan or duct. For very high power applications, it may be necessary to cool the chip directly with a heat pipe attachment, high-speed air jets, a direct heat sink attachment (cold plate), or dielectric liquid immersion. 

The pump occupies a volume of approximately 1 ft , with more specific dimensions as shown in Fig. 2. In order to minimize helium consumption, every effort has been made to shield the cold plate and its supply lines from thermal radiation of over 100°K. The cold plate is totally enclosed by chevrons and a conductance-cooled frame. The helium supply line is shielded from atmospheric temperature inside as well as outside of the chamber. This shield is cooled by liquid nitrogen lines. Outside of the chamber the shield also acts as a vacuum barrier. 

Whitenack, K., Demystifying Cold Plates, in Electronic Products, 2003, pp. 35-36. 27. Simmons, R.E., Direct Liquid Immersion Cooling for High-Power Density Microelectronics, in ElectronicsCooUng, 1996. 

Teflon support with its glass side facing the gas inlet the autoclave was evacuated (10 min, < 1 mbar), carefully filled with HCl gas (1 bar) and heated to 110°C for 15 min. After opening the autoclave the HCl vapors were blown out with a stream of cold air (5 min) and the HPTLC plate was cooled to room temperature. In order to intensify and stabilize the fluorescence the plate was dipped in a solution of liquid paraffin in chloroform (30 + 70) for 15 s. 

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