الفهرس 
The Rationale of Heat Transfer EnhancementOnly 14 pages are availabe for public view
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Abstract
Experiments are performed with a commercial gasketed plate heatexchanger (GPHE) with 30° chevron angle. The present study covers fourGPHE models. The first model is the conventional or base GPHE (withoutnano-particles and vibrations). The second model is GPHE with vibrationonly. The third model is GPHE with nano-particles only. Finally, the fourthmodel is GPHE with nano-particles and mechanical vibrations. In the 2ndmodel, mechanical, ultrasonic and acoustic as three different vibration typesare studied. In the 3rd model, ɣAl2O3-water nanofluid with four differentvolume fractions have been prepared and used as the hot working fluid. In the4th model, the effect of applying a low amplitude mechanical vibration on agasketed plate heat exchanger (GPHE), with γAl2O3-water nanofluid as acombined augmentation technique for heat transfer enhancement wasexperimentally studied. Applying the surface vibrations augments the heattransfer coefficients, while reduces the sedimentation of nanoparticles.According to the analysis of the results obtained from experimental study, themain conclusions from the present study can be summarized as follow:1- The heat transfer performance of the GPHE is enhanced when any type ofvibration is applied. The results revealed that at low amplitude mechanicalvibration is the most effective one.2- As a general trend, the HTC, OHTC and GPHE effectiveness are significantlyincrease as vibration intensity (represented by oscillation Reynolds number)increases.Chapter (5) 1693- The maximum values of percentage enhancement for convection heat transfercoefficient, overall heat transfer coefficient and GPHE effectiveness are 43%,31% and 18%, respectively with comparison with the non-vibrational case.These values have taken place after the resonance conditions at Reynoldsnumber oscillation = 211.34 and A/De = 52.66x10-3.4- Below grinding motor speed of 1800 rpm (i.e. at Reosc= 211.34), both vibrationfrequency and vibration amplitude are directly proportional to GPHE heattransfer enhancement ratio. However, for higher grinding motor speed,vibration frequency is increased and both vibration amplitude and GPHE heattransfer enhancement ratio are decreased.5- The maximum values of percentage enhancement for convection heat transfercoefficient, using ultrasonic and acoustic vibration are 11% and 6.9%,respectively with comparison with the non-vibrational case. These values havetaken place at an ultrasonic vibration frequency equal to 1 MHz and ultrasonicvibration intensity equal to 3.0 W/cm2 and a sound level equal to 108.10 dB,respectively.6- Using γAl2O3-water nanofluid as a working fluid in the hot loop enhances heattransfer performance of the GPHE with a relatively increase in pressure drop.7- The nanofluid convection heat transfer coefficient enhancement ratio increaseswith increasing nanofluid volume fraction and the maximum augmentation is14% at nanofluid volume fraction of (Φ𝑉= 0.51%).8- The influence of combined augmentation that includes the application ofnanofluid and vibration of heat transfer surface operating simultaneously onthe heat transfer performance enhancement is greater than that obtained byusing separable techniques working individually. 1709- The maximum augmentation in the 4th model (GPHE with nano-particles andmechanical vibrations) is grather than that for the 2nd model (GPHE withvibration only) and the 3rd model (GPHE with nano-particles only) by about21% and 50% respectively.10- The net convection heat transfer enhancement ratio is observed to be amaximum of 64%, when applied net augmentation of Al2O3-water nanofluidwith highest volume fraction of (Φ𝑉= 0.51%), and mechanical vibration withReynolds number oscillation (Reosc= 211.34).11- New empirical correlations for GPHE Nusselt number, for all studiedmodels with accepted maximum error percentage of 7.1 percent is obtained.12- For the 1st model of GPHE (stationary mode), the proposed correlationsshowed a good agreement with these found in the previous work.13- The pressure DROP is increased as nanofluid volume fraction is increased.The maximum percentage increase in the pressure DROP is 23.5%, whichachieved in the experiment of the largest volume fraction of (Φ𝑉= 0.51%).14- Not only vibration frequency, but also amplitude are responsible for heattransfer enhancement before occurrence of resonance (Reosc=209.32). Afterresonance takes place, only frequency continues increasing while amplitudedecreases; as a result, the heat transfer enhancement decreases.15- New GPHE friction factor correlation for both the 1st and the 2nd modelsare obtained with an acceptable error.