Circulation Heat Research Articles

Heat transfer rate and circulation rate in relation to angular and peripheral rotating speeds of scraper in mixing suspensions in a chamber-scraper vessel

Heat transfer rate and circulation rate in relation to angular and peripheral rotating speeds of scraper in mixing suspensions in a chamber-scraper vessel

The Effect of Heater Size, Location, Aspect Ratio, and Boundary Conditions on Two-Dimensional, Laminar, Natural Convection in Rectangular Channels

The effect of localized heating in rectangular channels was studied by solving the partial differential equations for the conservation of mass, momentum, and energy numerically using an unsteady state formulation and the alternating-direction-implicit method. The heating element was a long, horizontal, isothermal strip located in one, otherwise-insulated vertical wall. The opposing wall was maintained at a lower uniform temperature and the upper and lower surfaces were insulated or maintained at the lower temperature. Computations were carried out for Pr = 0.7, 0 ≤ Ra ≤ 105, a complete range of heater widths and locations and a wide range of aspect ratios. Flow visualization studies and comparison with prior computed results for a limiting case confirm the validity of the computed values. The computed rates of heat transfer and circulation provide guidance for locating heaters or coolers.

Energy Streamfunctions in the Vertical-Meridional Plane for the Northern Atmosphere

The zonal mean flux vector of atmospheric heat transports is very closely nondivergent in the vertical-meridional plane. This is demonstrated for potential (cpT + gz) and latent heat. Thus the heat flux vector fields can be represented by streamfunctions. The top of the atmosphere is a streamline for latent heat. For potential heat, the radiation flux across the top determines the upper boundary condition. The conservation equations are invariant with respect to arbitrarily choosing a constant reference heat but the streamfunctions are not. The impact on the streamfunctions of shifting the reference heat is equivalent to subtracting the mass transport, scaled with that constant, from the heat flux. To remove this ambiguity it is postulated that the curt of the heat flux vector in the vertical-meridional plane be minimized in the least-squares sense. This principle of minimum mean enstrophy is rationalized by analogy to electro-dynamics. It yields a formula for the reference heat in terms of hemispheric integrals of heat and mass flux curl. The formula is applied to the circulation statistics of the MIT-Library. The reference constants turn out to be numerically identical to the observed hemispheric annual mean of the respective heat form (∼324 J g−1 for potential heat and ∼6 J g−1, corresponding to 2.6 g kg−1, for latent heat). Streamfunctions reduced in this way are presented for the seasons. The potential heat circulation is highly variable. It changes sign from summer to winter over the entire northern atmosphere. The water circulation is less variable; it changes sign only in the tropics and fluctuates in intensity in the extratropics. It is shown that there is no further ambiguity in the streamfunction concept. The interrelationships between kinetic energy and potential, latent and static heat flux are discussed with the main result that the potential heat circulation is largely governed by radiation and precipitation flux but very little by the kinetic energy flux and not at all by the water vapor, and further that the streamfunction concept is not applicable to the kinetic energy flux. The main virtue of the streamfunctions is that they quantitatively represent the net heat flux on all scales and phases.

A Study of the Effect of Wind Shear on a Heat Island Circulation Characteristic of an Urban Complex

Simple linear models were used to study the effect of wind shear on the nocturnal urban heat island circulation. It was shown that the intensity of the urban heat circulation decreases by increasing the magnitude of the bulk shear through the boundary layer, if the heating rate is constant. However, if the difference between the mean temperature in the urban and environmental boundary layer and the stabilities are identical in two separate cases, the case with the stronger shear will have a stronger urban heat island circulation. When the magnitude of the vertical velocity was computed, it was found that the results were contingent on the boundary conditions used to solve the second-order equations for the motion. In the case where the perturbation vertical and horizontal velocities were set to zero at the surface, both the vertical scale and the intensity of the circulation approached infinity as the characteristic Richardson number approached zero. When the rigid lid concept was employed to limit the vertical scale of the circulation, a critical Richardson number existed in stable air for which the circulation had a finite maximum intensity. The value of the critical Richardson number was a function of the vertical scale of the rigid lid, and for a given vertical scale, there was more than one value for the critical Richardson number. The most intense circulation was found when the critical Richardson number was small.

Triangular, rhomboid and V distributed-resistance networks and their applications : S. C. Lee, IEEE Trans.PMP-4, June (1968), p. 41

Self-heat recuperation (SHR) technology has been proven to reduce exergy loss in different process systems, which lead to large energy savings due to its non-combustion process. The purpose of this research is to develop a novel self-heat recuperative heat circulation system using thermoelectric (TE) device as a heat circulator for gaseous and non-gaseous systems. The small ΔT usage of TE heat circulator enables the use of the high efficiency region of TE devices. A mathematical simulation of the performance of a TE heat circulator considering the effects of surface area, heat transfer coefficient and pellet height is presented in this study. Using a TE heat circulator with a surface area of 1 m2 to boil 1 kg of HFE-7100® an energy reduction of 82% was calculated compared to the conventional fired heater case.

Heat transfer coefficients and circulation rates for thermosiphon reboilers

AbstractHeat transfer coefficients and circulating data were obtained for a single tube thermosiphon reboiler operated under vacuum and at atmospheric pressure. The results are compared with existing correlations. an analysis is presented for local heat transfer coefficients in the single phase and two‐phase regions.

Circulation of heart to the hands of Arctic Indians.

Nine Indian men of an arctic village and eight urban white men have been compared in their responses to hand immersion in cold water. Following a 30-minute immersion in warm water (30°C) the hands were placed in cold water in an insulated bath (initially 5°C) for an additional 30 minutes. The rate of heat transfer to the water, finger skin temperatures and skin temperatures over a wrist vein were measured. All subjects were tested in this manner in two environmental situations: clothed in a warm room and unclothed in a cool room. In another experiment six Indians and five whites immersed their right hands in ice water while sitting confortably warm. Generally, the Indians showed a markedly superior ability to maintain hands warm in cold water. Their hands transferred more heat to the water whether the subjects were comfortably warm or chilly. In the cool environment hand heat loss was reduced in both groups, but the calculated heat transfer from circulation alone was still about twice as great in the Indians. The skin temperature measurements reflected the general trends of hand cooling and rewarming. The Indians withstood the hand immersion in ice water with quicker rewarming and less pain than the whites. Although their response is not conserving of metabolic heat, the loss is apparently trivial. The warming of the Indians' hands appears therefore to be adaptive in nature. Submitted on November 12, 1959

A STUDY OF THE HEAT FIELD OF THE ATMOSPHERE

Fundamental aspects of the heat balance of the atmosphere and of the atmospheric heat circulation are investigated. The distribution of heat amounts in different layers and in particular months is studied, and analytic expressions for the seasonal fluctuations of the heat distribution in the atmospheric layers are found. The annual heat turnover for different atmospheric layers and latitudinal zones is computed. New concepts, namely “heat potentials,” “pseudo-constant of circulation” and “coefficients of circulation” are introduced and explained. The approximate values of the circulation constant and of mean zonal coefficients are computed. The so-called “Schmidt paradox” is briefly discussed, and it is shown that the coefficients of circulation must be taken into account in every meteorological consideration. A revised concept of atmospheric circulation and a definition of the intensity of atmospheric circulation are deduced from the potential analysis of the heat field. An attempt is made to formulate general characteristics of the fluctuating heat field of the atmosphere.

British Food Journal Volume 44 Issue 8 1942

British Food Journal Volume 44 Issue 8 1942