Pool Boiling on Multiple Surfaces in Proximity

2005 ◽  
Author(s):  
Nasser Ghariban ◽  
Ali Rostami

Information on the boiling heat transfer on a surface when affected by the presence of other surfaces is scares. Pool boiling heat transfer process on multiple surfaces in proximity has been investigated in this work. In particular, the boiling curve and the critical heat flux on a surface located in the heated plume of another surface is studied experimentally. The surfaces are made of two identical wires with known diameter positioned horizontally in a predetermined short distance from each other. Tests were performed by heating the wires up to the critical heat flux in a pool of stationary FC-72 fluid. The boiling curves were experimentally developed for a surface when it is located in the plume of another heated surface. Initial results indicate that the critical heat flux on such a surface drops more than 30% compared to a single isolated wire. The change may be attributed to the plume effects on the bubble formation and bubble dynamics of upper surface as well as the effects on the degree of subcooling in the immediate neighborhood of the test surface. The research focused on the effects of spacing and the degree of subcooling on the boiling and the critical heat flux of the upper surface which is affected by the natural convection and boiling plume of the lower surface. The results of this project are expected to expand the existing knowledge of boiling heat transfer, particularly when it is affected by the presence of other surfaces in the proximity.

Author(s):  
Muhamad Zuhairi Sulaiman ◽  
Masahiro Takamura ◽  
Kazuki Nakahashi ◽  
Tomio Okawa

Boiling heat transfer (BHT) and critical heat flux (CHF) performance were experimentally studied for saturated pool boiling of water-based nanofluids. In present experimental works, copper heaters of 20 mm diameter with titanium-oxide (TiO2) nanocoated surface were produced in pool boiling of nanofluid. Experiments were performed in both upward and downward facing nanofluid coated heater surface. TiO2 nanoparticle was used with concentration ranging from 0.004 until 0.4 kg/m3 and boiling time of tb = 1, 3, 10, 20, 40, and 60 mins. Distilled water was used to observed BHT and CHF performance of different nanofluids boiling time and concentration configurations. Nucleate boiling heat transfer observed to deteriorate in upward facing heater, however; in contrast effect of enhancement for downward. Maximum enhancements of CHF for upward- and downward-facing heater are 2.1 and 1.9 times, respectively. Reduction of mean contact angle demonstrate enhancement on the critical heat flux for both upward-facing and downward-facing heater configuration. However, nucleate boiling heat transfer shows inconsistency in similar concentration with sequence of boiling time. For both downward- and upward-facing nanocoated heater's BHT and CHF, the optimum configuration denotes by C = 400 kg/m3 with tb = 1 min which shows the best increment of boiling curve trend with lowest wall superheat ΔT = 25 K and critical heat flux enhancement of 2.02 times.


Author(s):  
Seol Ha Kim ◽  
Gi Cheol Lee ◽  
Jun Young Kang ◽  
Kiyofumi Moriyama ◽  
Moo Hwan Kim ◽  
...  

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