scholarly journals THEORY OF INTENSIFIED HEAT EXCHANGE IN TURBULENT FLOW IN ANNULAR CHANNELS WITH TURBULATORS “LUG – GROOVE”

2015 ◽  
pp. 61-74
Author(s):  
Igor Lobanov ◽  
Keyword(s):  
Heat Exchange ◽  
Turbulent Flow ◽  
Annular Channels

Experimental Investigation on Flow Characteristics in a Tube-Bundle Channel

2012 ◽  
Author(s):  
Zhan Li ◽  
Guangyao Lu ◽  
Wenyuan Xiang
Keyword(s):  
Heat Exchange ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Circular Tube ◽  
Tube Bundle ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Flow Friction ◽  
Annular Channels ◽  
Flow Directions

Experiments were carried out to investigate the flow characteristics with/without heat exchange in vertical and inclined tube-bundle channels. In the experiments, the influences of flow directions and heat exchange upon the flow characteristics were studied. Experiments showed that the flow friction in tube-bundle channels had relations to the flow directions, and the liquid temperature difference at the inlet and outlet of tube-bundle channels. And these influences were comparatively obvious in the laminar flow regime. In the experiments, the transition from laminar to turbulent flow was carefully observed. The flow characteristics of single phase flow through tube-bundle channels were different from those in circular tubes and those in annular channels. The flow friction in tube-bundle channel is larger than that in normal circular tube. And the transition from laminar flow to turbulent flow in tube-bundle channel is different from that in normal circular tube. The influences of flow direction and heat exchange on the friction were also studied. The results were gained to provide the basis for the further investigations on the two-phase flow in tube-bundle channels.

scholarly journals HYDRODYNAMICS, DISTRIBUTION OF FLOWS AND THERMAL EFFICIENCY OF COIL HEAT EXCHANGERS IN UNITS OF HEAT-USING APPARATUS OF TUBE FURNACES

2019 ◽  
Vol 62 (4) ◽  
pp. 143-151
Author(s):  
Stanislav P. Sergeev ◽  
Faddey F. Nikiforov ◽  
Sergey V. Afanasiev ◽  
Juliya N. Shevchenko
Keyword(s):  
Heat Exchange ◽  
Turbulent Flow ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Heat Fluxes ◽  
Hydrodynamic Characteristics ◽  
Technological Problem ◽  
Tube Furnaces ◽  
Suction Or Injection ◽  
Coil Heat

The theoretical foundations of construction, mathematical description and engineering calculation of heat exchangers of the serpentine type in blocks of heat-using equipment of tube furnaces and other types of reactors designed for carrying out endothermic reactions (in particular, reforming of natural gas with water vapor) are considered. It is shown that the thermal efficiency of heat exchangers of the coil type is significantly affected by the correct choice of parameters ensuring a uniform distribution of energy flows over the surface of heat-resistant heat exchange tubes. This technological problem is solved by compiling the heat balance and selecting the system of the corresponding equations, which allows to calculate the temperature contour of the coil heat exchanger, its hydrodynamic characteristics and the distribution of mass and heat flows through the heat exchange tubes. The use of the tensor form of the Boussinesq hypothesis is considered, with which the Reynolds equation describing a turbulent flow is transformed to a partial differential equation for a single unknown function and its averaged form is obtained. In relation to the problem under consideration, the correctness of the chosen approach was confirmed both theoretically and experimentally. It is shown that in the core of a turbulent flow with an intense suction or injection, the liquid behaves almost as ideal and the well-known Helmholtz – Friedmann theorem holds with the necessary accuracy. From the aforementioned averaged equation, expressions are obtained that are suitable for describing heat fluxes in channels with suction or injection. According to this theoretical model, thermal calculations of coil-type heat exchangers were carried out, a more accurate assessment of the temperature of the heated medium in each coil tube was made, and the temperature gradient of the external heat carrier over the cross section of the gas duct was found. For the first time in the practice of calculations when choosing the parameters of coils, a number of boundary conditions were taken into account, such as the condition of the coil layout, the necessary heat exchange surface, permissible restrictions on hydraulic resistance, etc.

scholarly journals Study on turbulent flow in wave wall tube heat exchanger

2021 ◽  
Vol 2076 (1) ◽  
pp. 012025
Author(s):  
Liang Zhang ◽  
Anlong Zhang
Keyword(s):  
Heat Exchanger ◽  
Heat Exchange ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Average Pressure ◽  
Flow State ◽  
Tube Heat Exchanger ◽  
Exchange Performance ◽  
Straight Wall ◽  
Corrugated Structure

Abstract The traditional straight wall tube heat exchanger has low heat exchange efficiency, in order to solve this problem, the turbulent flow in wave wall tube heat exchanger was studied by numerical simulation. It is found that the unique corrugated structure of the heat exchange tube in the wave wall tube heat exchanger can improve the flow state of the fluid in the heat exchanger. The average pressure drop of heat exchanger gradually increases with the increase of Reynolds number Re. Under the same conditions, the average pressure drop of wave wall tube heat exchanger is lower than that of straight wall tube heat exchanger. The improvement of heat exchange performance of heat exchanger can not be realized only by increasing the inlet flow of heat exchanger. The wave wall tube heat exchanger can strengthen the heat exchange of the fluid in the heat exchanger.

Study on Mechanism of Condensation Heat Transfer of Water Jet in Steam Injector

2008 ◽  
Author(s):  
Takahiro Shimizu ◽  
Yuhki Takahashi ◽  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Toru Miyashita ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Turbulent Flow ◽  
Exchange Rates ◽  
Heat Transport ◽  
Water Jet ◽  
Steam Flow ◽  
Saturated Steam ◽  
Measured Velocity ◽  
Radial Heat

It has been proposed to introduce a steam injector into boiling water reactors as a feed water heat exchanger and a safety injection pump. In the present paper, the heat transfer characteristics in the steam injector were examined. The nozzle size of the water jet in the steam injector that was used in the present experiments was 5 mm. The length of the mixing section of the water jet and the steam flow in the injector was 53 mm. Subcooled water was supplied to the water nozzle. Saturated steam at approximately 0.1 MPa was also supplied to the mixing section of the steam injector. Water jet velocities tested in the present experiments were in the range of 9.7 ∼ 21 m/s. The velocities corresponded to the Reynolds number of 5.9×104 ∼ 1.5×105. Radial and axial temperature distributions of the water jet in the steam injector were measured. Velocity distributions of the water jet were also measured. From the measured temperature and the velocity distributions, heat exchange rates from the steam flow around the water jet to the water jet were derived. The obtained results indicated that the heat exchange rates were greatly larger than those of usual turbulent flow in a pipe. A flow state of the water jet was also visually examined. The results of the visual observation revealed that the interface between the water jet and the steam flow was very wavy. It was supposed that the wavy motion on the water jet surface created the effective-large-internal circulation flow in the water jet, which resulted in the tremendously effective heat transport into the center portion of the water jet. From the pictures of the water jet surface recorded by a high speed video camera, characteristics of waves on the surface; the wave height, the wave velocity, the wave length and the wave frequency, were obtained. The heat transfer of the water jet in the steam injector was correlated with the wave characteristic properties. The heat transfer of the water jet was also analyzed by using the commercial CFD code of STAR-CD. When the wavy interface was introduced into the STAR-CD code analysis, the radial heat transport was drastically improved. This analytical result also supported that the tremendously more effective radial heat transport than that of the usual turbulent flow was caused by the wavy motion of the water jet surface.

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