In case 1, two HTC (heat transfer coefficient) line are plotted one is only with heating andother one is with heating and vibration both.
HTC in case of vibration enhance comparedto normal heating HTC. But it is notable that enhancement of HTC with vibration due toChauhan, Eswaran and Reddy6enhancement in convection heat transfer. Enhancement in convection heat transfer isbecause vibration imposes fluid mixing. In case2, experiment is conducted in containerwhich top is opened to environment. Other specifications are similar to case 1. As case 2,two HTC (heat transfer coefficient) line are also plotted one is only with heating and otherone is with heating and vibration both. HTC in case of normal heating is comparativebetter than with vibration and heating case. It is not meant that the HTC is decreased incase of vibration but heat loss to environment is increased with vibration.
Free surface isvaried simultaneously with vibration hence interaction with environment is more. In case3, similar to case 2 excepting T3 is removed. It was introducing the effect of thermalstratification. As case 3, HTC lines for both cases with and without vibration reveal thateffect of stratification cannot be neglected.1001008070T1 for Heat with lid60T2 for Heat with lidT3 for Heat with lid50T4 for Heat with lidT1 for Heat w/o lid409090T2 for Heat w/o lidT3 for Heat w/o lid30T4 for Heat w/o lid050010001500Time ( sec )2000250080100015002000Time ( sec )Fig. 5 Comparative temperature plot for only Heat with and without lidFig. 4-Fig.
6 are shown the temperatures of thermocouples (T1, T2, T3 and T4) for bothwith and without lid study under vibration. Effect of the lid on temperature distribution isshown in Fig 4. The open experimental system which interacts with an environment iscompletely different from closed system having tab at the top to allow the steam out andmaintaining pressure as atmosphere. The temperature distribution can be divided into threeregions 1, 2 and 3. In region 1, heat transfer by convection is only therefore effect of lid isnot observed much in the temperature lines. In region 2, T2 has attended water saturationtemperature and onset nucleation started at heater surface. Due to onset nucleation, heattransfer rate increases which imposed to increase the temperature of fluid as lines T1, T3and T4. After few minutes, nucleate boiling also started and boiling heat transfer starts and7lines T1, T3 and T4 increases towards saturation temperature and attend that temperature.
When heat is continue supplied to system, bubby flow started. In case of open system,when nucleate boiling starts heat transfer rate increases however evaporation heat transferfrom system to environment also increases which not allowed the fluid temperature toattend the saturation temperature. Fig 5 shown that nucleate boiling comes earlier in caseof closed system than open system for normal heating experiment.1008010070T1 for Heat+Vib with lid60T2 for Heat+Vib with lidT3 for Heat+Vib with lid50T4 for Heat+Vib with lidT1 for Heat with lid40T2 for Heat with lidTemperature9090T3 for Heat with lid30T4 for Heat with lid05001000150020002500Time ( sec )80100015002000Time ( sec )Fig. 6 Comparative temperature plot for Heat+Vib and only Heat with lidIn fig 6, temperature distributions have shown for normal heating and heating withvibration when experimental system is closed from top. Temperature lines (T1, T2 and T4)are similar in case of vibration. However, in case of without vibration, T3 differ to T1, T2lines.
It shows that temperature is not propagated in the below portion of heater which isdue to stratification. However, in case of vibration, fluid mixing has come into picture,which suppresses the effect of stratification.ConclusionsThe behavior of the heat transfer in cuboid container with horizontal submerged cylindricalrod type cartridge heater subjected to vibration is investigated experimentally. The resultsreveal that the heat transfer coefficient is better when pool is subjected to vibrations thannormal heating.
Stratification is also suppressed due to increase in water mixing byvibration.