Thermal and flow measurements of continuous cryogenic spray cooling.
The performance of single sprays for high heat flux cooling using R-134a was studied. The heat flux and heat transfer coefficient at the surface of a sprayed jet based on measurements of steady-state temperature gradients on a thin copper plate during continuous spraying. Meanwhile, the spray droplets flow characteristics was also quantified through laser doppler velocimetry (LDV) measurements to obtain the local velocity distributions. The effects of mass flow rate and average droplet velocity, and spray exit-to-target distance on the surface heat flux including the corresponding critical heat flux (CHF) were explored through three different nozzle diameters of 0.2, 0.3, and 0.4 mm. Finally, the effective use of the fluid being delivered based on the cooling efficiency and cooling effectiveness was also examined. The relationship between CHF and nozzle performance in terms of cooling efficiency and cooling effectiveness was found. The heat transfer removal rate can reach up to 140 W/cm(2) for the present nozzle size of d (j)=0.2 and 0.3 mm, which may enhance the current cryogen spray cooling (CSC) technique that assists laser therapy of dermatoses.
Hsieh
Shou-Shing
SS
Department of Mechanical and Electro Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan, ROC. sshsieh@mail.nsysu.edu.tw
Tsai
Huang-Hsiu
HH
D017679:Cryotherapy / Q000295:instrumentation / Q000379:methods*; D062109:Dermatologic Surgical Procedures; D004867:Equipment Design; D006801:Humans; D066298:In Vitro Techniques; D053685:Laser Therapy / Q000295:instrumentation / Q000379:methods*; D012879:Skin Physiological Phenomena; D012881:Skin Temperature