Download or read book Study of Heat Transfer Under Impinging Jets for Freeze thaw Conditions written by Arnab Sarkar and published by . This book was released on 2002 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Improving the thermal Processing of Foods written by P Richardson and published by Elsevier. This book was released on 2004-07-16 with total page 527 pages. Available in PDF, EPUB and Kindle. Book excerpt: The application of heat is both an important method of preserving foods and a means of developing texture, flavour and colour. It has long been recognised that thermal technologies must ensure the safety of food without compromising food quality. Improving the thermal processing of foods summarises key research both on improving particular thermal processing techniques and measuring their effectiveness. Part one examines how best to optimise thermal processes, with chapters addressing safety and quality, efficiency and productivity and the application of computational fluid dynamics. Part two focuses on developments in technologies for sterilisation and pasteurisation with chapters on modelling retort temperature control and developments in packaging, sous-vide and cook-chill processing. There are chapters covering continuous heat processing, including developments in tubular heat exchangers, aseptic processing and ohmic and air impingement heating. The fourth part considers the validation of thermal processes, modelling heat penetration curves, using data loggers and time-temperature integrators and other new measuring techniques. The final group of chapters detail methods of analysing microbial inactivation in thermal processing and identifying and dealing with heat-resistant bacteria. Improving the thermal processing of foods is a standard reference book for those working in the food processing industry. Concisely explores prevailing developments in thermal technologies Summarises key research for improving food preservation techniques Analyses the effectiveness of methods used to enhance the quality of food

Download or read book Heat Transfer Under Impinging Jets at Very Close Jet to target Spacings written by Christopher J. Danek and published by . This book was released on 1995 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Study of Turbulent Heat Transfer from Confined Impinging Jets Using a Pseudo compressibility Method written by Mizanur Rahman and published by . This book was released on 1997 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of the Heat Transfer Resulting from a Heated Jet Impinging Upon a Cylinder written by Kevin William Whitaker and published by . This book was released on 1986 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer Characteristics Within an Array of Impinging Jets Effects of Crossflow Temperature Relative to Jet Temperature written by L. W. Florschuetz and published by . This book was released on 1985 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spanwise average heat fluxes, resolved in the streamwise direction to one stream-wise hole spacing were measured for two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate. The jet flow, after impingement, was constrained to exit in a single direction along the channel formed by the jet orifice plate and heat transfer surface. The crossflow originated from the jets following impingement and an initial crossflow was present that approached the array through an upstream extension of the channel. The regional average heat fluxes are considered as a function of parameters associated with corresponding individual spanwise rows within the array. A linear superposition model was employed to formulate appropriate governing parameters for the individual row domain. The effects of flow history upstream of an individual row domain are also considered. The results are formulated in terms of individual spanwise row parameters. A corresponding set of streamwise resolved heat transfer characteristics formulated in terms of flow and geometric parameters characterizing the overall arrays is described.

Download or read book Heat Transfer Characteristics Within an Array of Impinging Jets written by L. W. Florschuetz and published by . This book was released on 1985 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flow and Heat Transfers Associated with Impinging Jets in Crossflows written by and published by . This book was released on 1911 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis reports the results of an experimental study into the flow and heat transfers associated with both inclined and orthogonally impinging axisymmetric air jets. The majority of previously reported studies have been mainly confined to orthogonally impinging jets in stagnant surroundings. In this investigation, free jets as well as the effects of crossflows are considered. This investigation is Primarily concerned with local heat transfer variations. The experimental tests were. conducted with a single 12.7 mm diameter jet impinging on a flat surface, and heat transfers were evaluated using a heat-mass transfer analogy (t e Chilton-Colburn analogy). The sublimation of naphthalene was employed as the mass transfer technique. The flowfield associated with impinging jets has a significant influence on their heat transfer characteristics., In view of the present limited level of understanding of this 'complex' flowfield, extensive flow visualisation techniques were employed in this present investigation. Those were primarily intended to aid interpretation of the experimental heat transfer results, and also to provide further physical understanding of the flowfields resulting from the interactions between impinging jets and crossflowing streams. The flow and heat transfer tests conducted in the programme of work reported in this thesis covered typical ranges of flow parameters of interest in many practical applications of jet impingement systems. Jet inclinations of 45°, 600, and 90°, nozzle to target spacings of 2,11, and 8 nozzle diameters were studied. The Reynolds nuinbers were 30,200,32,700 and 55,100 and mass velocity ratios In the range 4.0 to 3.8 were studied. The effects of these parameters on the flow and heal transfers associated with impinging jets are reported. Comparisons were drawn between the heat transfer results and those of previously reported studies where appropriate.

Download or read book Convective Heat Transfer Under a Turbulent Impinging Slot Jet at Large Temperature Differences written by Debmalya Das and published by . This book was released on 1982 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer from Normally Impinging Two dimensional Air Jets written by Donald Gene Arganbright and published by . This book was released on 1971 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of the Heat Transfer of Two Parallel Jets Impinging Normal to a Flat Surface written by Nicholas Rudenko and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The recent development of fifth generation fighter aircraft has been designed to takeoff in short distances, accelerate to supersonic flight, and land vertically. For short takeoff and vertical landing operations, STOVL, aircraft use thrust vectoring to direct high-speed, high temperature jet exhaust from the primary nozzle towards the ground. This redirection of flow provides approximately half of the thrust required for lift. The remaining thrust is generated by a lift fan which produces a sonic jet plume. The complex nature of the flow-field generated by these aircraft severely impacts the surrounding operational environment. The need to understand the high temperature, high velocity flow-field associated with these aircraft in close proximity to the ground is extremely important. These flow conditions give rise to hazardous conditions for personnel and equipment in the nearby proximity of the landing aircraft.To understand the effects of high temperature impinging flows and the subsequent heat transfer into the impingement plane, the existing High Speed Aeroacoustics Laboratory was redesigned to achieve high temperatures flows while in impinging configurations. High temperature flows are achieved through the use of two electric heaters in a parallel configuration. The parallel heater configuration allows the jet exhaust on an impinging jet model to reach a total temperature ratio of 2.0 with a jet Mach number of 1.34. More importantly, the use of electric heaters and PID controllers produces stable flow conditions within 4 K of the desired jet temperature.Once facility development was completed, a series of experiments were conducted to determine the flow-field characteristics of a heated, supersonic rear jet impinging on a ground plane. A dual impinging jet model (using a cold, sonic front jet) was also studied. This model is representative of a generic military-style STOVL aircraft in a hover configuration. The operational conditions were limited to jet stand-off distances between 4 and 15 nozzle diameters, and jet Mach numbers between 1.16 and 1.56. The total temperature of the jet was also varied between 1.2 and 2.0.Schlieren flow visualization was used to qualify the average flow-field behavior exhibited in both single and dual jet configurations. Single jet configurations showed a strong relationship between jet stand-off distances and thickness of the thermal outwash. For dual jet configurations, the interaction between the two jets, and the subsequent mixing, can be seen. The location of this mixing region is strongly dependent on the Mach number of the rear jet.Steady-state and transient surface temperature measurements were also a focus in this study. Steady-state measurements were compared to adiabatic wall temperatures calculated from CFD. For the limited CFD cases, experimental results compared well with the calculations, with less than 10% difference at all locations. For single impinging jets, the normalized temperature distribution in the impingement region is heavily dependent upon the jet separation distance. For large separation distances, increases in the total temperature ratio can reduce the peak normalized temperature at the stagnation point by as much as 10%. For dual impinging jet operations, the region between the two jets experience an increase in normalized temperature when compared to the single jet operations. A slight increase in the stagnation temperature is also seen.Transient thermal distributions obtained for a rear jet Mach number of 1.16 at a total temperature of 1.5 and a jet separation distance of 6 nozzle diameters are compared to a transient conduction computation model. The experimental model compared poorly to the experimental model for all time increments. However the differences can be attributed to boundary condition assumptions, and accuracy can be improved with model refinement.

Download or read book Experimental and Numerical Investigation of Turbulent Heat Transfer Due to Rectangular Impinging Jets written by and published by . This book was released on 2005 with total page 706 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to their efficient heat and mass transfer potential, impinging jets have received attention in various applications. Heat transfer and flow characteristics of rectangular turbulent impinging jets issued from a 24:1 aspect ratio and 24:1 contraction ratio nozzle were investigated experimentally and numerically. In the heat transfer measurements; a thin stainlessƯ-steel foil was utilized to obtain isoƯflux boundary conditions on the impingement surface. The target plate was free to translate in the lateral direction and the heat transfer distributions were determined at 0d"/Wd"0 with the microƯ-thermocouples placed underneath the foil. The measurements were conducted for Re=8900-48600 at nozzleƯ-to-Ưtarget spacing of 0.5d"/Wd"2.0. Both semi and fully confined jets were investigated. Heat transfer coefficients at Re=28100, 36800, 45600 and H/W=4.0 were determined by using adiabaticƯ-wall temperatures and the distributions were compared with those of the wall shear stress. Off-center peaks were observed at high Re and low H/W. Since the wall distributions are susceptible to nozzleƯ-exit conditions, velocity and turbulence profiles at the nozzleƯ-exit were measured for the velocity range of interest. Additionally, near-Ưwall mean velocity and turbulence profiles were determined at Re=21500 and 36800 at H/W = 4.0 to have a better understanding of the secondary peaks in the wall distributions. Numerical computations were performed by using several different turbulence models (k-#, k-#, V2F and Reynolds stress models). In wallƯ-bounded turbulent flows, near-Ưwall modeling is crucial. Therefore, the turbulence models eliminating wall functions such as the k-# and V2F models may be superior for modeling impingement flows. The numerical results showed reasonable agreement with the experimental data for local heat transfer and skin friction coefficient distributions. The occurrence of the secondary peaks was predicted by the k-# and V2F models, and for a few cases with the low-Re-k-# models. Near-Ưwall measurements along with the computed profiles were used to describe the s̀̀econdary peak'' phenomena. It was shown that the increase in turbulence production in the wallƯ-streamwise direction enhances turbulent momentum and heat transport in the wall-Ưnormal direction which lead to secondary peaks in the wall distributions. The possibility of improving surface heat transfer with fully-Ưdeveloped jets was also explored numerically as a case study.

Download or read book Heat Transfer from Swirling Impinging Jets written by and published by . This book was released on 1904 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is concerned with the determination of the local and average mass/heat transfer--from swirling jets impinging orthogonally onto flat surfaces. ApplicatioCn> of swirl alters the flow field of the' jet considerably and eventually the maximum velocity in the jet is displaced from the axis resulting in a typical 'double-peak' profile. Further increase of swirl, can even result in a recirculation in the inner core of the flow. The turbulence characteristics of the jet are also affected. it is expected that these changes will, in addition, modify the heat transfer behaviour. Consequently, a study of both single free jets and a square array (of 3x 3) of jets was undertaken. The range of swirls examined in this study was from zero through to weak and then medium swirl, i. e. the swirl number S was varied from 0 to 0.48. The other parameters varied in the experiments were the nozzle-to-target spacing z/D from 2 to 12, the nozzle pitches x/D (for arrays of jets) which were 3.2,4.8 and 6.4, and the jGt Reynolds number. In the single frce jet tests, two flow rates corresponding to ReD-":2 32pOOO and 60,000 were studied whilst, for the 'multiple' jets, the measurements were confined. to the lower of these Reynolds numbers. (ReD is based on the mean exit velocity in the non-swirling case and the diameter of the nozzle.) Limited velocity and turbulence measurements were also undertaken on the single jet to characterise the flow and also to compare the behaviour of the present jets with those in previous studies. The flows were similar to those observed previously for swirling jets so that the heat transfer results should be generally applicable. A 'thin-film' naphthalene sublimation technique was used to measure mass transfers over the target surface. The heat transfer coefficients were then derived using the Chilton-Colburn analogy. A rig was developed to spray a uniform coating of naphthalene on the target surface. This 'thin-film' technique was found to provide re.

Download or read book Heat Transfer from Impinging Jets A Literature Review written by Peter Hrycak and published by . This book was released on 1981 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report is a literature survey of the state-of-the-art of heat transfer from impinging air jets. Over 70 references are cited.

Download or read book Heat Transfer Enhancement by Turbulent Impinging Jets written by Mami Kumagai and published by . This book was released on 2000 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer from an Enhanced Surface Subject to Non circular Impinging Jets with Cross Flow written by Jamison William Janawitz and published by . This book was released on 1998 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer from Swirling Impinging Jets written by M. Mahmood and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is concerned with the determination of thelocal and average mass/heat transfer--from swirling jetsimpinging orthogonally onto flat surfaces. ApplicatioCn>of swirl alters the flow field of the jet considerablyand eventually the maximum velocity in the jet is displacedfrom the axis resulting in a typical double-peak profile. Further increase of swirl, can even result in arecirculation in the inner core of the flow. The turbulencecharacteristics of the jet are also affected. itis expected that these changes will, in addition, modifythe heat transfer behaviour. Consequently, a study of both single free jets and asquare array (of 3x 3) of jets was undertaken. Therange of swirls examined in this study was from zerothrough to weak and then medium swirl, i. e. the swirlnumber S was varied from 0 to 0.48. The other parametersvaried in the experiments were the nozzle-to-targetspacing z/D from 2 to 12, the nozzle pitches x/D (forarrays of jets) which were 3.2,4.8 and 6.4, and the jGtReynolds number. In the single frce jet tests, two flowrates corresponding to ReD-":2 32pOOO and 60,000 were studiedwhilst, for the multiple jets, the measurementswere confined. to the lower of these Reynolds numbers.(ReD is based on the mean exit velocity in the non-swirlingcase and the diameter of the nozzle.)Limited velocity and turbulence measurements were alsoundertaken on the single jet to characterise the flowand also to compare the behaviour of the present jetswith those in previous studies. The flows were similarto those observed previously for swirling jets so thatthe heat transfer results should be generally applicable. A thin-film naphthalene sublimation technique was usedto measure mass transfers over the target surface. Theheat transfer coefficients were then derived using theChilton-Colburn analogy. A rig was developed to spraya uniform coating of naphthalene on the target surface. This thin-film technique was found to provide repeatableresults and the validity of the experiments was further assessed by comparing the results with previouslypublished data for the no swirl case. These were inreasonable agreement. For the single free jets, the application of swirl wasfound to continuously reduce the heat transfers. Theheat transfers, however, became more uniform. An empiricalcorrelation has also been suggested for the averageNusselt number associated with these single swirling jets and is valid for S= 0.12-to 0.48. In some circumstancesin the multiple jet tests (e. g. at close nozzle-to-target spacings) the average heat transfers increasedto a maximum of IS =0.24 (approximately). Further increasesin the degree of swirl brought about a subsequentreduction in average heat transfer coefficients untileventually the performance of the swirling jets was poorerthan that of the non-swirling flows. This discrepancyin behaviour can be explained in terms of changes in thelocal heat transfer distributions.