Showing papers on "Concentric tube heat exchanger published in 1978"

Direct contact heat exchanger with phase change of working fluid

Abstract: A direct contact thermal storage heat exchanger which utilizes the liquid-vapor phase change of a working fluid within the heat exchanger, and energy generation systems incorporating the heat exchanger. The heat exchanger is particularly useful in combination with a solar energy receiver. The heat exchanger includes an insulated pressure vessel packed with pebbles or spheres. Working fluid in the vapor phase from a solar heat source enters the unit and condenses, transferring thermal energy to the pebbles. The liquid level of working fluid about the pebbles is decreased during this mode of operation. When it is desirable to release this stored energy the liquid level is increased, and the energy is transferred to the working fluid which forms a vapor, and can be used to drive a turbine or other prime movers.

Heat exchange enhancement structure

Abstract: A passive heat exchange enhancement structure which operates by free convection includes a flat mounting portion having a plurality of integral fins bent outwardly from one side edge thereof. The mounting portion is securable around a stovepipe, to a flat surface or the like for transferring heat from the pipe through the fins to the surrounding air by rotation-enhanced free convection.

Water heater temperature control system

Abstract: A water heater supplies hot water at a variable flow rate, depending on demand, and at a substantially constant, controlled temperature It comprises a heat exchanger formed with an inlet and an outlet whereby water can be supplied to and withdrawn from the heat exchanger in accordance with demand and means for passing a second fluid such as steam through the heat exchanger coil to heat the water A temperature gradient is thus established in the water in the direction of its flow through the heat exchanger A sense tube forms a substantially homogeneous mixture of different portions of the water, these portions being drawn from sampling points spaced apart along the temperature gradient and in relative proportions depending on the flow rate of the water through the heat exchanger The temperature of the water in the sense tube is detected, and control means responds to the sensed temperature for controlling the rate at which steam is supplied to heat the water Thus a combined set point and feed forward control is established that minimizes fluctuations in the temperature of the hot water as withdrawn for end uses by anticipating changes in BTU requirements

Heat exchanger support construction

Abstract: A heat exchanger of the shell and tube type having a floating tube sheet to accommodate differential thermal expansion and contraction between the shell and the tubes. The cross-sectional area of sliding joint means between the floating tube sheet and the shell, and the total external and internal cross-sectional areas of the tubes, are selected to minimize axial forces on the tubes. A novel tube support system including hollow support members engaged between the adjacent tubes enables a true counterflow heat exchange relationship to be established between the shell side fluid and the tube side fluid.

Thermal design of a heat exchanger for heating or cooling blood.

Abstract: Experimental data, and their correlation with predictions from theory, are presented for the thermal design of a countercurrent heat exchanger for heating or cooling blood. The thermal design considers the influence on the Nusselt number of blood and the heat exchanger effectiveness of variables such as the blood flow rate, tube diameter and length, and the thermal properties of blood. The data presented are compared with data from the literature and with predictions from theory. Insofar as the design of a blood heat exchanger is concerned, flowing blood can be considered a single-phase fluid. Some applications of the thermal design analysis, the production and control of blood hyperthermia or hypothermia are discussed.

Local heat transfer coefficients in scraped-film heat exchanger

Abstract: The instantaneous heat transfer coefficients in a scraped-film heat exchanger have been determined using the electrochemical technique for a two-bladed, 78.7mm I.D. exchanger. The time-averaged local heat transfer coefficients were found to agree fairly well with previous work of Azoory and Bott, though some variation in liquid flow rate was detected. The timeaveraged local Nusselt number was found to be represented by Nu=Q.15(Rer•Pr)1/2Reawwith a=(l-3.74×10-2N)/9. The variation of heat transfer coefficient with time was observed to be very different from that predicted by the accepted model for the phenomena based upon unsteady state conduction.

Concentric Annular Ducts

Abstract: This chapter discusses concentric annular ducts for laminar flow. The concentric circular annular duct is an important geometry for many fluid flow and heat transfer devices. The simplest form of a two-fluid heat exchanger is a double pipe made up of two concentric circular tubes. One fluid flows through the inside tube, while the other fluid flows through the annular passage. The chapter presents the analysis of the heat transfer and fluid friction problems for developing and developed profiles for a variety of boundary conditions for both the circular tube and concentric annular duct. Depending upon the temperature or heat flux specified at the inner and outer surfaces of the annulus, there are four possible fundamental boundary conditions. For each kind of fundamental boundary condition, there are two solutions of the energy equation, one for each of the two surfaces heated, thus totaling eight heat transfer solutions. The fundamental boundary conditions of the fourth and fifth kinds are identical for concentric annular ducts heated symmetrically around each periphery.

Heat exchanging apparatus and method

Abstract: A heat exchanging apparatus for reducing the temperature of a heating fluid prior to thermal communication with a heated fluid. The apparatus includes an integral pre-cooling heat exchanger located within a main heat exchanger. The pre-cooling heat exchanger brings the heating fluid into thermal communication with the heating fluid circulating in the main heat exchanger so that the heated fluid is prevented from departing from nucleate boiling in the main heat exchanger.

Stack-type heat exchanger

Abstract: A stack-type heat exchanger having a complementary fan section in attached communication with a heat exchanger tube section, the fan section forcing incoming air through heat exchanger tubes having a damper plate at or adjacent their output ends to generate a positive air pressure in the tubes at a value above and in excess of the pressure of vented stack gases passing through the heat exchanger tube section chamber from and to lower and upper portions of said stack.

Coupled conduction-turbulent convection in a circular tube

Abstract: An analysis for hydrodynamically and thermally fully developed heat transfer in a circular tube coupled with heat conduction in the tube wall is presented. The energy equations for the fluid and solid body are solved simultaneously under the conditions of continuity in the heat flux and temperature at the interface. Circumferential as well as radial temperature gradients are permitted in both energy equations along with internal heat generation in the tube wall. Solution of the equations are found by the method of separation-of-variables along with superposition of particular solutions. As an application, cooling of the first wall in a fusion reactor is considered. Comparisons of temperature profiles in the tube wall are made for high (aluminum) and low (stainless steel) thermal conductivity materials. Comparisons are also made under the assumption that radial temperature gradients are negligible.