摘要:

ABSTRACTAn experimental study was made of heat transfer by natural convection inside packed vertical cylinders whose wall temperatures varied sinusoidally with time. The packings were small glass or plastic spheres with water as the interstitial fluid. The purpose of this research was to stimulate, in a controlled laboratory model, the heat transfer to grain stored in bins.Temperature distributions throughout the bed were determined for various sizes of packing, several height‐to‐diameter ratios, and for a number of frequencies of sinusoidal forcings. The results are presented graphically in terms of the amplitude ratios of the interior temperatures to the wall temperature and the phase lag between the interior and wall temperatures. The operating conditions ranged from essentially pure conduction to moderately strong natural convection.The temperature distributions near the wall of the cylindrical container were found to be predicted by a simple one‐dimensional model. Temperature distributions throughout an entire packed bed were quite complex when there was significant natural convection and, although general overall predictions were possible, accurate calculation of the temperature at a specific location and time was impos

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1983.tb00296.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTHeat transfer in a water‐cooled scraped surface heat exchanger has been investigated. The overall heat transfer coefficient in the heat exchanger is composed of three elements: heat transfer coefficient in the coolant jacket, resistance to heat flow in the separation wall and heat transfer coefficient inside the scraped cylinder.A method for assessing the heat transfer coefficient at the coolant side was developed.In contrast with studies published elsewhere, heat transfer was investigated with food systems which are non‐newtonian and possess a complicated and unknown flowing behavior at higher shear rates.For water and three starch‐based food products (starch content 12–18%) the heat transfer coefficients inside the scraped cylinder were measured for shaft speeds ranging from 1.67 to 10 revolutions/s. The experimental results were compared with heat transfer coefficients calculated with a model based on the penetration theory. For the starch‐based products, in general, no consistent interactions between mass flow rates and internal heat transfer coefficients were observed. In the shaft speed range studied heat transfer coefficients at scraped surface varied from 3200 to 7800 W/m2K for water, from 500 to 3150 W/m2K for velouté sauce, from 670 to 1330 W/m2K for roux and from 780 to 1900 W/m2K

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1983.tb00297.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTConcentrated CaCl2and LiCl brines were used to evaporatively concentrate liquid foods. The concentration was carried out in double falling film evaporators in which brine flowed down the outside of the tubes and liquid food flowed down the inside. The vapor spaces between the brine and the food were connected and vapor from the food was absorbed in the brine. The heat generated by vapor absorption in the brine provided the heat needed to sustain evaporation, and was transferred to the food because of the boiling point elevation of the brine. Evaporation rates approaching those obtained in commercial evaporators were obtained for skim milk, sugar solutions and orange juice. The evaporation rates were affected by flow rates, temperature, concentration and tube material.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1983.tb00298.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTA calculation method for batch washing of cottage cheese curd which yields combinations of washing time and ratio of water volume to curd volume is presented. The method is based on a theoretical model of the washing process which showed mass transfer of whey solids, rather than heat transfer, to be the rate limiting step. Input values include initial and final values of total solids concentration in the whey entrapped in the curd, and curd and water temperatures. Selection of optimum time and water volume depends on subsequent economic analysis.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1983.tb00299.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY