PubMed · 15309806
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Carina Dennis. 2004-08-05. Cooling off.. https://pubmed.ncbi.nlm.nih.gov/15309806/
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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.
BACKGROUND AND OBJECTIVES: Extended-pulse dye lasers (EPDL) are commonly used to treat a variety of vascular lesions. This study evaluated whether differences in pulse formats and cooling methods might affect outcome in the treatment of small facial telangictasia. STUDY DESIGN/MATERIALS AND METHODS: Ten subjects presenting with symmetric, bilateral facial telangiectasia were studied. Each side of the face was treated with either the V-Startrade mark smart-cool air cooling (Cynosure, Inc.) (VS) or V-beam DCD cooling (Candela, Inc.) (VB) EPDL treatments with both systems were undertaken with a 10-milliseconds pulse duration, 1 J/cm(2) below the purpuric threshold, with up to three passes. RESULTS: Treatment clearance with the VS EPDL occurred with a lower fluence, using fewer passes than with the VB EPDL (P < 0.05). CONCLUSIONS: Although both the currently popular EPDL systems are highly effective in the treatment of small facial telangiectasia, clinical differences can be seen between these two systems.
BACKGROUND AND OBJECTIVES: Although cryogen spray cooling (CSC) in conjunction with laser therapy has become the clinical standard for treatment of port wine stain (PWS) birthmarks, the current approach does not produce complete lesion blanching in the vast majority of patients. The objectives of this study are to: (1) experimentally determine the dynamic CSC heat flux when a skin phantom is preheated, and (2) numerically study the feasibility of using skin preheating prior to CSC to improve PWS laser therapeutic outcome. STUDY DESIGN/MATERIALS AND METHODS: A fast-response thin-foil thermocouple was used to measure the surface temperature and thus heat flux of an epoxy skin phantom during CSC. Using the heat flux as a boundary condition, PWS laser therapy was simulated with finite element heat diffusion and Monte Carlo light distribution models. Epidermal and PWS blood vessel thermal damage were calculated with an Arrhenius-type kinetic model. RESULTS: Experimental results show that the skin phantom surface can be cooled to a similar minimum temperature regardless of the initial temperature. Numerical simulation indicates that upon laser irradiation, the epidermal temperature increase is virtually unaffected by preheating, while higher PWS blood vessel temperatures can be achieved. Based on the damage criterion we assumed, the depth and maximum diameter of PWS vessels that can be destroyed irreversibly with skin preheating are greater than those without. CONCLUSIONS: Skin preheating prior to CSC can maintain epidermal cooling while increasing PWS blood vessel temperature before laser irradiation. Numerical models have been developed to show that patients may benefit from the skin preheating approach, depending on PWS vessel diameter and depth.