Implementation of heat exchanger performance testing system of heat transfer and flow resistance

A heat transfer performance testing system is presented with its hardware structure, operation principle, and software control and measurement system. Working fluids of the subsystem include thermal conducting oil, compressed air, glycol water solution and water as the heating fluids, and air and water as the cooling fluids. The heat transfer performance testing of heat exchangers can be conducted not only for a conventional one heating fluid to one cooling fluid, but also for a compound air cooling heat exchanger with two or three heating fluids in parallel or in series. The control and measurement system is implemented based on a LabVIEW software platform, consisting of the data acquisition and process system, and the automotive operation and control system. By using advanced measuring instruments combined with sound computer software control, the testing system has characteristics of a compact structure, high accuracy, a wide range of testing scope and a friendly operation interface. The uncertainty of the total heat transfer coefficient K is less than 5%. The testing system provides a reliable performance testing platform for designing and developing new heat exchangers.

Experimental Analysis of Performance of Heat Exchanger with Plate Fins and Parallel Flow of Working Fluids

Heat exchangers are devices in which heat is transferred from one fluid to another fluid as a result of temperature difference. Heat exchanger presented in the current paper in which inside the tubes flows water, but outside the tubes flows air aims to enable cooling of circulating water, which serves to cool the engine of a machine. Such exchangers find application in the automotive industry as well as heating and cooling equipment and HVAC systems etc. The surface of the heat exchanger by the air side always tends to be much larger using surface fins in order to facilitate equalization of thermal resistance for both sides of the heat exchanger, because the rate of transmission of heat from the water side is much greater. Furthermore, the paper will present analytical and experimental studies involved for determination of performance of plate-fin heat exchanger for various flows of working fluids in order to get the highest values of performances i.e.: overall heat transfer coefficient U, efficiency of heat exchanger ε, maximal and real heat transferred, pressure drop, air velocity and Reynolds number from the air side of heat exchanger etc. The present scientific paper is based on the fact that from the experimental model made for laboratory conditions, conclusions are derived that can be used during installation of such heat exchanger on certain machines in order to predict their performance.

Performance Simulation of a Double Tube Heat Exchanger Based on Different Nanofluids by Aspen Plus

A heat exchanger’s performance depends heavily on the operating fluid’s transfer of heat capacity and thermal conductivity.Adding nanoparticles of high thermal conductivity materials is a significant way to enhance the heat transfer fluid’s thermal conductivity.This research used engine oil containing alumina(Al_(2)O_(3))nanoparticles and copper oxide(CuO)to test whether or not the heat exchanger’s efficiency could be improved.To establish the most effective elements for heat transfer enhancement,the heat exchangers thermal performance was tested at 0.05%and 0.1%concentrations for Al_(2)O_(3)and CuO nanoparticles.The simulation results showed that the percentage increase in Nusselt number(Nu)for nanofluid at 0.05%particle concentration compared to pure oil was 9.71%for CuO nanofluids and 6.7%for Al_(2)O_(3)nanofluids.At 0.1%concentration,the enhancement percentage in Nu was approximately 23%for CuO and 18.67%for Al_(2)O_(3)nanofluids,respectively.At a concentration of 0.1%,CuO nanofluid increased the LMTD and overall heat transfer coefficient(U)by 7.24 and 5.91%respectively.Both the overall heat transfer coefficient(U)and the heat transfer coefficient(hn)for CuO nanofluid at a concentration of 0.1%increased by 5.91%and 10.68%,respectively.The effectiveness(εn)of a heat exchanger was increased by roughly 4.09%with the use of CuO nanofluid in comparison to Al_(2)O_(3)at a concentration of 0.1%.The amount of exergy destruction in DTHX goes down as Re and volume fractions go up.Moreover,at 0.05%and 0.1%nanoparticle concentrations,the percentage increase in dimensionless exergy is 10.55%and 13.08%,respectively.Finally,adding the CuO and Al_(2)O_(3)nanoparticles improved the thermal conductivity of the main fluid(oil),resulting in a considerable increase in the thermal performance and rate of heat transfer of a heat exchanger.

Numerical investigation of grooves effects on the thermal performance of helically grooved shell and coil tube heat exchanger

Heat exchangers are integral parts of important industrial units such as petrochemicals,medicine and power plants.Due to the importance of systems energy consumption,different modifications have been applied on heat exchangers in terms of size and structure.In this study,a novel heat exchanger with helically grooved annulus shell and helically coiled tube was investigated by numerical simulation.Helically grooves with the same pitch of the helical coil tube and different depth are created on the inner and outer wall of annulus shell to improve the thermal performance of heat exchanger.In the first section,thermal performance of the shell and coil heat exchanger with the helical grooves on its outer shell wall was compared with same but without helical grooves.At the second section,helically grooves created on both outer and inner wall of the annulus shell with different groove depths.The results showed that the heat exchanger with grooves on both inner and outer shell wall has better thermal performance up to 20%compared to the heat exchanger with grooves on only outer shell wall.The highest thermal performance achieves at lower flow rates and higher groove depths whereas the pressure drop did not increase significantly.

Research on the falling film flow and heat transfer characteristics of FLNG spiral wound heat exchanger under sea conditions

As the key equipment of floating liquefied natural gas(FLNG)process,the performance of spiral wound heat exchanger(SWHE)influences operation costs and reliability of the whole system.The sea conditions destroy the falling film flow state of the refrigeration and then affect the heat transfer performance of FLNG SWHE.In order to design and optimize the SWHE,a cryogenic experimental device of FLNG process and a numerical model of falling film flow have been constructed to study the effects of sea conditions on the falling film flow and heat transfer characteristics of SWHE.The cryogenic experimental results show that the pitching conditions have larger effects on the heat transfer performance than yawing.Under the pitching angle of 7°,the natural gas temperature and gaseous refrigerant temperature increase by 3.22°C and 7.42°C,respectively.The flow rates of refrigerant and feed natural gas have a great impact on the heat transfer performance of SWHE under pitching and compound sloshing conditions.When the tilt angle increases to 9°,the tube structure with outer diameter D=8 mm and pipe spacing S=4 mm is recommended to reduce the drying area of the pipe wall surface.

A numerical study on heat transfer enhancement and design of a heat exchanger with porous media in continuous hydrothermal flow synthesis system

The aim of this study is to use a new configuration of porous media in a heat exchanger in continuous hydrothermal flow synthesis(CHFS)system to enhance the heat transfer and minimize the required length of the heat exchanger.For this purpose,numerous numerical simulations are performed to investigate performance of the system with porous media.First,the numerical simulation for the heat exchanger in CHFS system is validated by experimental data.Then,porous media is added to the system and six different thicknesses for the porous media are examined to obtain the optimum thickness,based on the minimum required length of the heat exchanger.Finally,by changing the flow rate and inlet temperature of the product as well as the cooling water flow rate,the minimum required length of the heat exchanger with porous media for various inlet conditions is assessed.The investigations indicate that using porous media with the proper thickness in the heat exchanger increases the cooling rate of the product by almost 40% and reduces the required length of the heat exchanger by approximately 35%.The results also illustrate that the most proper thickness of the porous media is approximately equal to 90% of the product tube's thickness.Results of this study lead to design a porous heat exchanger in CHFS system for various inlet conditions.

Investigation of a Counter Flow Microchannel Heat Exchanger Performance with Using Nanofluid as a Coolant

In this paper the performance of a counter flow microchannel heat exchanger (CFMCHE) is numerically investigated with a nanofluid as a cooling medium. Two types of nanofluids are used Cu-water and Al2O3-water. From the results obtained it’s found that thermal performance of CFMCHE increased with using the nanofluids as cooling medium with no extra increase in pressure drop due to the ultra fine solid particles and low volume fraction concentrations. The na-nofluids (Cu-water and Al2O3-water) volume fractions were in the range 1% to 5%. It’s also found that nanoflu-id-cooled CFMCHE could absorb more heat than water-cooled CFMCHE when the flow rate was low. For high flow rates the heat transfer was dominated by the volume flow rate and nanoparticles did not contribute to the extra heat absorption. Also the performance of CFMCHE can be increased considerably by using nanofluids with higher thermal conductivities.

Analysis of secondary flow in shell-side channel of trisection helix heat exchangers

The flow characteristics of shell-side fluid in the tube-and-shell heat exchangers with trisection helical baffles with 35° inclined angles are numerically analyzed. The secondary flow distribution of the fluid in the shell-side channel is focused on. The results on meridian planes indicate that in the shell-side channel, the center part of fluid has an outward tendency because of the centrifugal force, and the peripheral region fluid has an inward tendency under the centripetal force. So in a spiral cycle, the fluid is divided into the upper and lower beams of streamlines, at the same time the Dean vortices are formed near the left baffle, and then the fluid turns to centripetal flow near the right baffle. Finally the two beams of streamlines merge in the main flow. The results of a number of parallel slices between two parallel baffles with the same sector in a swirl cycle also show the existence of the secondary flow and some backward flows at the V-gaps of the adjacent baffles. The secondary flows have a positive effect on mixing fluid by promoting the momentum and mass exchange between fluid particles near the tube wall and in the main stream, and thus they will enhance the heat transfer of the helix heat exchanger.

Numerical and experimental study on the falling film flow characteristics with the effect of co-current gas flow in hydrogen liquefaction process

Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat exchanger structure and hydrogen liquefaction process(LH2). The methods of cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the falling film flow characteristics with the effect of co-current gas flow in LH2spiral wound heat exchanger.The results show that the flow rate of mixed refrigerant has a great influence on liquid film spreading process, falling film flow pattern and heat transfer performance. The liquid film of LH2mixed refrigerant with column flow pattern can not uniformly and completely cover the tube wall surface. As liquid flow rate increases, the falling film flow pattern evolves into sheet-column flow and sheet flow, and liquid film completely covers the surface of tube wall. With the increase of shear effect of gas-phase mixed refrigerant in the same direction, the liquid film gradually becomes unstable, and the flow pattern eventually evolves into a mist flow.

Research on shell-side heat and mass transfer with multi-component in LNG spiral-wound heat exchanger under sloshing conditions

The spiral-wound heat exchanger(SWHE) is the primary low-temperature heat exchanger for large-scale LNG plants due to its high-pressure resistance, compact structure, and high heat exchange efficiency. This paper studied the shell-side heat and mass transfer characteristics of vapor-liquid two-phase mixed refrigerants in an SWHE by combining a multi-component model in FLUENT software with a customized multicomponent mass transfer model. Besides, the mathematical model under the sloshing condition was obtained through mathematical derivation, and the corresponding UDF code was loaded into FLUENT as the momentum source term. The results under the sloshing conditions were compared with the relevant parameters under the steady-state condition. The shell-side heat and mass transfer characteristics of the SWHE were investigated by adjusting the component ratio and other working conditions. It was found that the sloshing conditions enhance the heat transfer performance and sometimes have insignificant effects. The sloshing condition is beneficial to reduce the flow resistance. The comprehensive performance of multi-component refrigerants has been improved and the improvement is more significant under sloshing conditions, considering both the heat transfer and pressure drop.These results will provide theoretical support for the research and design of multi-component heat and mass transfer enhancement of LNG SWHE under ocean sloshing conditions.

Numerical Simulation of Liquified Natural Gas Boiling Heat Transfer Characteristics in Helically Coiled Tube-in-Tube Heat Exchangers

Helically coiled tube-in-tube(HCTT)heat exchangers are widely applied to the process technology because of their compactness and higher heat transfer efficiency.HCTT heat exchangers play an important role in liquified natural gas(LNG)use and cold energy recovery.The heat transfer characteristics,pressure distribution,and degree of vaporization of LNG in HCTT heat exchangers are numerically investigated.By comparing the simulation results of the computational model with existing experimental results,the effectiveness of the computational model is verified.The numerical simulation results show the vapor volume fraction of the HCTT heat exchanger is related to the inlet Reynolds number,inner tube diameters,and helix diameter.The vapor volume fraction increases rapidly from the fourth to the seventh equal division points of the helix tube length.On condition that the inlet Reynolds number is greater than 33500,the pressure drop rate gradually increases.When the magnitude of the vapor volume fraction is below 0.2,the heat transfer coefficient increase rate is greater than that when the vapor volume fraction is above 0.2.The heat exchange efficiency of HCTT heat exchangers increases with the decrease of the ratio of helix diameter to inner tube diameter.

Distribution performance of gas–liquid mixture in the shell side of spiral-wound heat exchangers

The non-uniformity of gas–liquid mixture is a critical issue which leads to the heat transfer deterioration of spiralwound heat exchangers(SWHEs).Two-phase mass flow rate and the content of gas are important parameters as well as structural parameters which have prominent influences on flow distribution uniformity of SWHE shell side.In order to investigate the influences of these parameters,an experimental test system was built using water and air as mediums and a novel distributor named"tubes distributor"was designed.The effects of mass flow rate and the content of gas on two-phase distribution performance were analyzed,where the mass flow rate ranged from 28.4 to 171.9 kg·h-1 and the content of gas changed from 0.2 to 0.8,respectively.The results showed that the mixture mass flow rate considerably influenced the liquid distribution than that of gas phase and the larger mass flow rate exhibited the better distribution uniformity of two-phase flow.It was also found that the tubes distributor had the better two-phase uniformity when the content of gas was around 0.4.Tube diameter played an important role in the distribution of gas phase and slit width was more significant for the uniformity of liquid phase.

Numerical Simulation and Optimization of a Mid-Temperature Heat Pipe Exchanger

In this paper,we take the mid-temperature gravity heat pipe exchanger as the research object,simulate the fluid flow field,temperature field and the working state of heat pipe in the heat exchanger by Fluent software.The effects of different operating parameters and fin parameters on the heat transfer performance of heat exchangers are studied.The results show that the heat transfer performance of the mid-temperature gravity heat pipe exchanger is the best when the fin spacing is between 5 mm and 6 mm,the height of the heat pipe is between 12 mm and 13 mm,and the inlet velocity of the fluid is between 2.5 m/s to 3 m/s.

Fluid flow and heat transfer characteristics of spiral coiled tube: Effects of Reynolds number and curvature ratio

Numerical analysis was performed to investigate flow and heat transfer characteristics in spiral coiled tube heat exchanger. Radius of curvature of the spiral coiled tube was gradually increased as total rotating angle reached 12n. As the varying radius of curvature became a dominant flow parameter, three-dimensional flow analysis was performed to this flow together with different Reynolds numbers while constant wall heat flux condition was set in thermal field. From the analysis, centrifugal force due to curvature effect is found to have significant role in behavior of pressure drop and heat transfer. The centrifugal force enhances pressure drop and heat transfer to have generally higher values in the spiral coiled tube than those in the straight tube. Even then, friction factor and Nusselt number are found to follow the proportionality with square root of the Dean number. Individual effect of flow parameters of Reynolds number and curvature ratio was investigated and effect of Reynolds number is found to be stronger than that of curvature effect.

Performance comparison for oil-water heat transfer of circumferential overlap trisection helical baffle heat exchanger

The performance tests were conducted on oil–water heat transfer in circumferential overlap trisection helical baffle heat exchangers with incline angles of 12°, 16°, 20°, 24° and 28°, and compared with a segmental baffle heat exchanger. The results show that the shell side heat transfer coefficient h_o and pressure drop Δp_o both increase while the comprehensive index h_o/Δp_o decreases with the increase of the mass flow rate of all schemes. And the shell side heat transfer coefficient, pressure drop and the comprehensive index ho/Δpo decrease with the increase of the baffle incline angle at a certain mass flow rate. The average values of shell side heat transfer coefficient and the comprehensive index h_o/Δp_o of the 12° helical baffled scheme are above 50% higher than those of the segmental one correspondingly, while the pressure drop value is very close and the ratios of the average values are about 1.664 and 1.596, respectively. The shell-side Nusselt number Nu_o and the comprehensive index Nu_o·Eu_(zo)^(-1) increase with the increase of Reynolds number of the shell side axial in all schemes, and the results also demonstrate that the small incline angled helical scheme has better comprehensive performance.

Comparison of heat transfer performances of helix baffled heat exchangers with different baffle configurations

Numerical simulations were performed on flow and heat transfer performances of heat exchangers having six helical baffles of different baffle shapes and assembly configurations, i.e., two trisection baffle schemes, two quadrant baffle schemes, and two continuous helical baffle schemes. The temperature contour or the pressure contour and velocity contour plots with superimposed velocity vectors on meridian, transverse and unfolded concentric hexagonal slices are presented to obtain a full angular view. For the six helix baffled heat exchangers,the different patterns of the single vortex secondary flow and the shortcut leakage flow were depicted as well as the heat transfer properties were compared. The results show that the optimum scheme among the six configurations is a circumferential overlap trisection helix baffled heat exchanger with a baffle incline angle of 20°(20°TCO) scheme with an anti-shortcut baffle structure, which exhibits the second highest pressure dropΔpo, the highest overall heat transfer coefficient K, shell-side heat transfer coefficient hoand shell-side average comprehensive index ho/Δpo.

Design Optimization of Shell and Tube Heat Exchanger by Vibration Analysis

In this paper a simplified approach to optimize the design of Shell Tube Heat Exchanger [STHE] by flow induced vibration analysis [FVA] is presented. The vibration analysis of STHE helps in achieving optimization in design by prevention of tube failure caused due to flow induced vibration. The main reason for tube failure due to flow induced vibration is increased size of STHE. It is found that in case of increased size of STHE, the surface area and number of tubes increases, thus the understanding and analysis of vibration becomes a very difficult task. Again it is found that flow induced vibration analysis is considered as an integral part of mechanical & thermal design of STHE. The detailed design, fabrication, testing and analysis work was carried out at Alfa Laval (India), Ltd., Pune-10.

Development and Experimental Study on Heat Exchanger with High Efficiency of Mining Machinery

The flow patterns, pressure drop, and heat transfer characteristics of shell and tube heat exchangers with different shell side structure were studied systematically by experiments. Experiments show that the optimal angle of helical baffle is 40°, and the optical porosity of porous media is 0. 985. Based on this, a new oil cooler was developed for hydraulic system of mining machinery, and its heat trausfer coefficient is higher than that of the existing oil coolers.

Effects of Heat Exchange Tube Structural Parameters on Performance of Vehicle Radiator

In order to improve the performance of vehicle radiators, a two-dimensional heat transfer steady-state model of the radiator was set up. The influence of the structural parameters (axial ratio) of the heat exchange tube on the windward side on the heat transfer performance of the radiator was studied. With the increase of the axial ratio of the heat exchange tube on the windward side, the heat exchange capacity of the heat exchange tube surface slightly decreases. The heat exchange area increases significantly, which increases the total heat exchange of the radiator and improves the heat transfer performance of the radiator. When the axial ratio increases from 1.0 to 2.0, the average surface heat transfer capacity decreases from 5664.16 W/m2 to 5623.57 W/m2.

Performance Assessment of Heat Exchangers for Process Heat Integration

Pinch Analysis is an attractive solution for reduction of thermal energy costs in thermo-chemical industries.In this approach,maximum internally recoverable heat is determined and a heat exchange network is designed to meet the recovery targets.The thermal performance of a heat exchanger over its lifetime is however a concern to industries.Thermal performance of a heat exchanger is affected by many factors which include the physical prop-erties of the shell and tube materials,and the chemical properties of the heat transferfluid.In this study,thermal performance of shell and tube heat exchangers designed to meet heat recovery targets in a Pinch Analysis study is simulated.The aim of this paper is to present predictions of thermal performances of shell and tube heat exchan-gers with different heat transferfluids and geometries as they undergo fouling degradation.Engineering approaches based on thermodynamic analysis,heat balance and Kern Design equations,as well as what-if simu-lation modeling are used in this work.Shell and tube heat exchangers were designed to meet internal heat recov-ery targets for three process plants,A,B and C.These targets were published in a separate paper.The effects of degradation of the tubes-due to incremental growth of fouling resistance-on thermal performance of the exchan-ger were simulated using Visual Basic Analysis(VBA).Overall,it was found that growth in fouling reduces ther-mal efficiency of shell and tube heat exchangers with an exponential relationship.An increase of 100%of fouling resistance leads to an average reduction of 0.37%heat transfer.Higher values of logarithmic mean temperature difference(LMTD)and higher ratios of external diameter to internal diameter of the exchanger tubes amplify the effect of fouling growth on thermal performance of the exchangers.The results of this work can be applied in pinch analysis,during design of heat exchangers to meet the internal heat recovery targets,especially in predicting how fouling growth can affect these targets.This can also be useful in helping operators of shell and tube heat exchangers to determine cleaning intervals of the exchangers to avoid heat transfer loss.