Comparative study of intermittent spray cooling in single and two phase regimes
Comparative study of intermittent spray cooling in single and two phase regimes
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DOI：
10.1016/j.ijthermalsci.2013.06.008
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发表时间：
2013-12-01
影响因子：
4.5
通讯作者：
Tay, A. A. O.
中科院分区：
文献类型：
--
作者：
Somasundaram, Sivanand;Tay, A. A. O.
喷雾冷却系统具有多种应用，如冷却铸钢件，食品工业中的冷冻，高功率电子设备，激光和航空电子系统的冷却。间歇喷雾冷却（ISC）工艺是一种以一定频率和一定开放周期脉冲喷射的高级工艺。这种多功能喷雾过程可以使用质量流量，频率和占空比（一个周期内打开时间的百分比）进行调整，以匹配目标所需的冷却速率。ISC的一个主要优点是它有效地利用了冷却剂，因此能源效率高于传统的喷雾。本工作的目的是比较低热流通量去除率下单相体系与高热流通量去除率下两相体系的ISC过程。实验使用连接电磁阀的商用喷嘴（TG SS 0.3喷涂系统公司）进行。冷却液是水，绝缘铜块的上表面作为冷却目标。电磁阀采用闭环反馈控制，根据测得的铜块表面温度对电磁阀进行控制。实验在不同的热流状态下进行，分别为11、22、33（低热流状态，单相）、55、88（过渡状态）、108、125和149 W/cm(2)（高热流状态，两相）。实验还进行了不同的喷雾压力- 2,4和6巴。利用逆热传导问题，通过序列函数估计方法估计了瞬态传热系数。因此，有可能估计在喷淋的开启和关闭期间的传热。在较低的热通量下，占空比在20 - 70%之间，在中等热通量下，占空比增加到60-90%的范围，在高热通量下，占空比在40-85%的范围内。较高的占空比导致较低的间歇周期频率。当表面温度接近冷却剂的沸点时，在中热流密度和高热流密度下，存在显著的相变，与连续喷雾冷却相比，这导致了显著的冷却剂节约。在两相状态下，即使在喷淋期间，传热系数也很高，从而最大限度地利用了可用能量。在高热通量时，温度波动也急剧减小。(C) 2013 Elsevier Masson SAS。版权所有。
Spray cooling systems have diverse applications like cooling steel castings, cryo freezing in food industries, cooling of high power electronics, lasers and avionics systems. An intermittent spray cooling (ISC) process is an advanced process where the spray is pulsed at a certain frequency and with a certain open period. This versatile spray process can be adjusted using the mass flow rate, frequency and duty cycle (percentage of open time in one cycle) to match the required cooling rate on the target. One major advantage of ISC is that it utilizes the coolant effectively and therefore the energy efficiencies are higher than conventional sprays. The objective of the present work is to compare the ISC process in the single-phase regime at low heat flux removal rates with that in the two-phase regime at high heat flux removal rates. The experiments were conducted using a commercial nozzle (TG SS 0.3 Spraying systems Co) connected to a solenoid valve. The coolant fluid was water and the top surface of an insulated copper block served as the cooling target. The solenoid valve was controlled by closed-loop feedback control, based on the measured surface temperature of the copper block. The experiments were conducted at different heat flux regimes - 11, 22, 33 (low heat flux, single phase regime), 55, 88 (transitional regime), 108, 125 and 149 W/cm(2) (high heat flux, two phase regime). The experiments were also conducted for various spray pressures - 2, 4 and 6 bar. The transient heat transfer coefficient was estimated using an inverse heat conduction problem through a sequential function estimation method. Thus it was possible to estimate the heat transfer during the on and off periods of the spray. At lower heat fluxes the duty cycle was between 20 and 70% and at moderate heat fluxes the duty cycle increased to a range of 60-90% and at high heat fluxes duty cycles were in the range of 40-85%. A higher duty cycle led to a lower frequency of the intermittent cycles. At medium and high heat fluxes when the surface temperature was near the boiling point of the coolant, there was significant phase change and this led to significant coolant savings compared to continuous spray cooling. In the two phase regime the heat transfer coefficient was high even during the spray off periods and resulted in utilization of the available energy to the maximum extent. Also at high heat fluxes the temperature fluctuations reduced drastically. (C) 2013 Elsevier Masson SAS. All rights reserved.