Study of the mechanism of surface cooling by air-assisted water spray in the convective heat exchange conditions

Аuthors

Demidov A. S.¹, Zakharenkov A. V.¹, Komov A. T.¹, Dedov A. V.²

1. National Research University «Moscow Power Engineering Institute», Krasnokazarmennaya str., 17, bldg. 1G, Moscow, 111250, Russia
2. Moscow Power Engineering Institute (National Research University), 14, Krasnokazarmennaja St., Moscow, 111250, Russia

Abstract

Spray cooling is an effective cooling method, however, in modern literature very little attention is paid to the study of cooling by air-assisted water spray created by a pneumatic nozzle. This paper describes an experimental installation for the study of cooling by air-assisted water spray. The results of experiments conducted on surface cooling with a spray created by two different pneumatic nozzles differing in the flow section of the water channel are presented. During the experiments, the mass flow rate of water through the nozzle varied in the range of 8–25 g/s at a pressure of 100–380 kPa, and the mass flow rate of air was 0,3–2 g/s at a pressure of 80–400 kPa. The average cooling surface temperature was 20–100 °С. The surface was heated using an electron beam cannon, the area of the heated surface was 20x40 mm2. The studied cylindrical sample with a radius of 30 mm and a thickness of 14 mm was installed in a vacuum-dense experimental module located in a vacuum chamber. 9 thermocouples were installed in the copper sample, which made it possible to estimate the radial heat distribution and 4 local values of the wall temperature and heat flux. In addition to the local values of the heat flux, the average value of the dissipated heat flux was also calculated based on the amount of heat input and the cooling surface area. Based on the averaged values, the heat transfer coefficient was determined. Based on the calculated values, a criterion equation is constructed using the Nu and We numbers, the ratio of air and water pressures, the relative gas content, and the ratio of the Prandtl numbers of water at the wall temperature and the temperature at the nozzle inlet. The obtained criterion equation Keywords: heat transfer, spray cooling, pneumatic nozzle, air-assisted water spray, heat flux, heat transfer coefficient, non-dimensional equation, experimental study

References

1. Pitts RA, Carpentier S, Escourbiac F et al. Physics basis and design of the ITER plasma-facing components. Journal of Nuclear Materials. 2011;415: 957–964.

2. Hamann HF, Weger A, Lacey JA et. al. Hotspot-Limited Microprocessors: Direct Temperature and Power Distri-bution Measurments. IEEE Journal of Solid-State Cir-cuits. 2007;1(42):56–65.

3. Mudawar I, Valentine VS. Determination of the Local Quench Curve for Spray-Cooled Meatllic Surfaces. Journal of Heat Treating, 1989;7:107–121.

4. Kasatkin AP, Komov AT, Skorodumov SV et. al. Inzhe-nernye i fizicheskie probelmy termoyadernoi ehnergetiki. 1992;(657):45–48. (In Russ.).

5. Balitskii AV. The technology of manufacturing vacuum equipment. Moscow. Energiya. 1966. p. 312. (In Russ.).

6. Groo DA, Tupotilov DA, Demidov AS. Radioehlektro-nika, ehlektrotekhnika i ehnergetika. Moscow. 2023. p. 761. (In Russ.).

7. Aleksandrov AA, Grigor'ev BA. Tables of thermophysi-cal properties of water and steam. Moscow. 1999. p. 168. (In Russ.).

8. Sychev VV, Vasserman AA, Kozlov AD et. al. Thermo-dynamic properties of air. Moscow. Izdatel'stvo standar-tov; 1978. p. 276. (In Russ.).

9. Ghodbane M, Holman JP. Experimental study of spray cooling with Freon-113. International Journal of Heat and Mass Transfer. 1991;(34):1163–1174.

10. Isachenko VP, Kushnyrev SI. Jet cooling. Moscow. Ehnergoatomizdat; 1984. p. 216. (In Russ.).

11. Estes KA, Mudawar I. Correlation of Sauter mean diameter and critical heat flux for spray cooling of small surfaces. International Journal of Heat and Mass Trans-fer. 1995(38):2985–2996.

12. Cheng WL, Han FY, Liu QN et al. Spray characteristics and spray cooling heat transfer in the non-boiling re-gime. Energy. 2011;(36):3399–3405.

13. Groo DA, Demidov AS, Zakharenkov AV et. al. Analysis of the effectiveness of cooling a high-temperature sur-face with a dispersed coolant flow. Thermal Engi-neering. 2024;71(9):761–775. (In Russ.).