Local heat transfer under an array of micro jet impingement using HFE-7000

We studied the transient local surface temperature response that occurs when jet impinging of nitrogen gas is applied to the surface to which a pulsating heat flux is applied. After manufacturing a micro jet impinging device, which was composed of three parts--a silicon wafer, a vinyl sticker, and a Pyrex wafer--nitrogen gas was used as working fluid and the velocity was 344.8 m/s, corresponding jet Reynolds was 1467. And the amplitudes of heat fluxes varied from 5.67 to 16.17 W/cm 2 , the frequency also varied from 0.1 to 1000 Hz, then temperature response of RTDs was acquired. For example, when a heat flux, 8.5 W/cm 2 , was applied with a frequency of 0.1 Hz, the highest and lowest temperatures of RTD located on the center of the heater and under indirect jets were 30.2 °C and 20.7 °C. From the acquired results, the time constant of the device was estimated between 17 ms and 32 ms, and this result shows the conjugated mode of conduction and convection of heat transfer. To understand the dominant heat transfer, we decoupled the conduction mode and the convective heat transfer mode through analytical calculations and confirmed that the time constants were 11 μs and 128 ms, respectively. In addition, the heat transfer coefficient was inversely calculated through numerical calculation by simulating the RTD manufactured in the device, and through this, it was confirmed that the dimensionless time constant was related to the Nu number and the correlation was developed as / t τ − = ≤

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“…Accordingly, the orifices were considered as converging nozzles. More details are given in Shin et al [22].…”

Section: Package and Devicementioning

confidence: 99%

Analysis of transient temperature response under micro jet impinging using nitrogen (N2)

Shin

Kim

2021

J Mech Sci Technol

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“…In the case of impingement of miniaturized jets or microjets several experimental and numerical works were conducted. These investigations concentrated on both characterization of heat transfer and fluid flow during microjet impingement [10] as well as investigation of performance of devices based on the microjet impingement technology, e.g., cooling system of gas turbine blade [11], silicon-based heat sink for electronic applications [12], modular heat exchanger [13] and cooling system integrated within an electronic devices [14].…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of a cooling of a hot plate by an array of microjets

Łapka

Cieplniński

2019

E3S Web Conf.

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In this paper heat transfer during impingement of an array of 8×8 microjets on a hot surface was investigated. The influence of a ratio of a distance between a nozzle and hot plate (H/d) and microjet diameter-based Reynolds number (Red) on the temperature and heat transfer coefficient (HTC) on the hot plate were numerically studied. The numerical model which was based on the steady-state compressible Navier-Stokes equations and SST k-ω turbulence model was developed and applied for the analysis. During simulations the ratio of the distance between the nozzle and hot plate to the microjet diameter was H/d = 3.125, 25 and 50, while the microjet diameter-based Reynolds number was equal to Red = 690, 1100 and 1510. The ratio of the microjet pitch to the microjet diameter was s/d = 31.25. It was found that both the H/d ratio and Red significantly influenced flow patterns in the gap between the nozzle and hot plate as well as the temperature and HTC on the surface of the hot plate. With increase of the H/d ratio a more uniform distributions of the plate temperature and HTC were observed, while the rise in the Red intensified heat transfer on the hot plate.

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