Heat Transfer Coefficient Of Tube Research Articles

Effect of temperature sampling methods on sphere packed tube heat transfer coefficient determination

This paper investigates the heat transfer characteristics and the pressure drop of a sphere packed tube using Computational Fluid Dynamics (CFD) simulation. The turbulent kinetic energy of the fluid exhibits significant variation based on the differing accumulation structures of the particles, which is deemed to greatly influence the heat transfer characteristics. Consequently, the temperature distribution at the outer wall becomes inhomogeneous. Previous studies have overlooked the relative positioning between the thermocouples and the particles, potentially leading to inaccurate estimations of the heat transfer coefficient and discrepancies between CFD simulations and real-world experiments. To address this, two temperature sampling methods are employed in this paper to estimate the heat transfer coefficients: one method involves measuring the temperatures at various sampling positions, while the other uses the surface average temperature of the packed area as the sample temperature. Interestingly, it is found that different temperature sampling methods significantly impact the heat transfer coefficients. This study serves as a reminder for future research on sphere packed tubes to prioritize temperature sampling positions.

Suggestion of Correlations to Obtain Shell and Tube Side Nusselt Numbers in Coiled Heat Exchangers

In coiled tube heat exchangers increase in curvature ratio and effective contact of shell fluid with coil surface led to better thermal characteristics. This work addresses study of thermal performance, shell and tube heat transfer coefficients (ho and hi). Also, mathematical correlations are predicted to obtain shell and tube Nusselt numbers (Nuo and Nui). In the designing of compact coiled heat exchangers consisting of straight helical coil (SHC), conical coil (CC) and spiral coil knowledge of Nuo and Nui is necessary whereas mathematical correlation to calculate Nuo considering variations in shell geometry is not found. Five heat exchangers consisting of three cone coils (angle, ϴ = 30°, 50° and 70°), spiral coil (ϴ = 0°) and SHC (ϴ = 90°) are tested. Using Wilson plot method ho and hi are obtained for wide range of tube side Reynolds numbers (Rei = 3700 - 21000). It is observed that, highest ho is obtained for ϴ = 30°CC with better thermal performance. Lowest ho is obtained for ϴ = 90°SHC. Ratio of height of shell, Hs and diameter of shell, Dso is considered in prediction of single correlation as: Nuo = 16.55.Reo0.55.Pro0.4 *(Hs/Dso)0.096. Comparison with experimental findings shows variation of 0-14%. Similarly two correlations are proposed as: Nui = 0.0512.Rei0.80.Pri0.4.CRave0.18 and Nui = 0.0365.Dei0.815.Pri0.4.CRave-0.3. A fair agreement is found with existing researchers.

Experimental Research on Heat Transfer Performance of CO2 Tube Bundle Falling Film Evaporator

Abstract CO2 is a promising refrigerant substitute, and falling film evaporator is widely used in high-capacity heat pump systems. In this article, a CO2 heat pump experimental device is built. According to experimental parameters, a CO2 falling film heat exchanger is fabricated. The falling film heat exchanger is used in heat pump evaporator, and its heat transfer characteristics are analyzed and tested. The outer diameter of the heat exchanger is 219 mm, outer diameter of the inner tube is 15.88 mm, and total outer surface area of the inner tube is 0.58 m2. Number of internal tubes was 12, each with a length of 0.97 m. During the test, change of heat transfer coefficient of each tube was analyzed when evaporation temperature, CO2 mass flowrate, and heat flow density changed. The influence of the position of heat exchange tube inside falling film evaporator on heat transfer coefficient is analyzed. The order of heat transfer coefficient of internal heat exchange tube is obtained. Finally, database of CO2 falling film evaporator is established. Through data sorting, heat exchange correlation formula is obtained. The deviation of 90% data in database is less than 5%. Heat exchange correlation formula has good accuracy.

Experimental comparison on condensation and evaporation outside double-side enhanced horizontal tubes

Experimental investigations of the condensation and evaporation of R410A on the outside of two double-side enhanced heat transfer tubes were conducted, and the tube performance was compared with that of a smooth copper tube. The research object consisted of a smooth tube with a length of 2000 mm and an outer diameter of 25.4 mm and two double-side enhanced tubes of the same size. The evaporation experiments were run under the following conditions: the evaporation saturation temperature was 7°C, water inlet temperature was 8°C–18°C, and water flow rate was 0.6–1.6 m3/h. The condensation experiments were run under the following conditions: the saturation temperature was 35°C, water inlet temperature was 21°C–30°C, and water flow rate was 0.4–1.6 m3/h. During the data processing, the heat transfer coefficient of the water side was obtained using the Gnielinski-Wilson method, and that of the refrigerant side was obtained using the thermal resistance separation method. The effect of the surface structure on the heat transfer performance was analyzed, and a strengthening measure was proposed. The experimental results indicate that the evaporation heat transfer coefficients outside the smooth tube increased with the raise of the inlet water temperature, while the double-side enhanced tubes decreased; both the condensation heat transfer coefficients outside the smooth tube and the enhanced tubes increased with the increase of the water flow rate. Due to the different type of enhanced tube ribs, tube #3 surface structure is more conducive to the formation of vaporization core, which is about 30% higher than the outer heat transfer coefficient of tube #2. It is more in line with the requirements of strengthening horizontal single tube external pool boiling heat transfer. In the condensation experiment, the condensation heat transfer coefficients outside the smooth tube increased with the raise of the inlet water temperature, while the double enhanced tubes decreased; both the condensation heat transfer coefficients outside the smooth tube and the enhanced tubes increased with the increase of the water flow rate. With the analysis of the rib structure, the outer surface structure of tube #2 has stronger drainage capacity, and the external average condensation heat transfer coefficient is about 7% higher than that of tube #3, which is more in line with the requirements of condensing heat transfer outside the single tube.

Falling film evaporation experiment and data processing method of R1234ze (E) on horizontal enhanced tubes

For two kinds of specially made enhanced tubes with outer diameters of 19 and 25 mm, the falling film evaporation experiment was carried out by using environmental refrigerant R1234ze (E) under the experimental condition that the water velocity in the tube was controlled from 1 to 3.5 ms−1. "The Wilson-Gnielinski Separation Method" and "The Wilson-Gnielinski-Heat Flux Correction Method" were used to process the experimental data. The comparative analysis showed that when the heat fluxes of all the test points outside the tube were constant, the results of two calculation methods were almost the same. When the heat fluxes of all the test points outside the tube were fluctuant, the results of two calculation methods were different and the heat flux correction method should be applied to reduce the error. The enhanced tube with outer diameter of 19 mm was used to investigate the heat transfer performance of falling film evaporation, with spray density ranging from 0.03 to 0.1 kgm−1 s−1, heat flux ranging from 15 to 45 kWm−2 and evaporation temperature ranging from 0 to 25 °C. And the enhancement rate inside the tube was obtained by using the heat flux correction method. Finally, the variation trends of the overall heat transfer coefficient and the outside tube heat transfer coefficient under different working conditions were both obtained experimentally and analyzed theoretically.

Evaporation heat transfer characteristics of falling film in small diameter fabricated tubes of absorption refrigeration system: An experimental investigation

Absorption refrigeration system is going through optimization. The evaporator is one of the core components of the absorption refrigeration system, and its optimization can be done by improving the wettability and reducing the uneven distribution of liquid film. Enhanced tubes are often helpful in mitigating the film thickness and ensuring proper wetting of the tubes, thus enhancing the heat transfer performance. Using a smaller tube diameter also significantly affects the heat transfer performance because of the increasing ratio of the developing boundary layer to the fully developed boundary layer. In this study, seven small-diameter (12.7 mm) tubes were used to optimize the performance of the evaporator. The parameters observed are as follows: falling-film Reynolds number (10–100), wall superheat (2.2–5.1 °C), and saturation pressure (0.9–1.20 kPa). The heat transfer coefficient exhibited a peak point at a falling-film Reynolds number, called transition Reynolds number (Retransition) mostly at a value of ~42. The wall superheat is increased by increasing the wall temperature and, as a result, the heat transfer coefficient remains unchanged; however, the heat flux increases almost linearly. The heat transfer coefficient increases with the increase in the saturation pressure. One of the fabricated tubes was tested with corrosion, and a negligible change in the heat transfer coefficient was observed when compared with the uncorroded tube. Both droplet and jet modes are observed when viewing the falling-film phenomena through a glass window. Smooth tube data reveal a reasonable comparison with the jet and droplet mode of Hu et al. Of all the tubes, the heat transfer coefficient of Tube_Z is the highest. Tube_Y1 exhibited the highest heat flux; however, Tube_Z exhibited the highest ratio of heat flux to friction factor. Empirical correlations were developed based on the current experimental perimeters, and correlations predicted the data within ±20%.

LNG 냉열을 회수하기 위해 재킷 냉각수를 열원으로 하는 유기랭킨사이클의 열교환기 설계

In this study, the thermal design of the evaporator and condenser in the ORC system using the jacket cooling water as the high temperature heat source and the cooling heat of LNG as the low temperature heat source was carried out. R134a was used as the working fluid for the ORC system. In the case of the evaporator, Shah"s correlation shows the lowest heat transfer coefficient among the two-phase flow heat transfer coefficients in tubes obtained from the literature. It was found that the contribution of nuclear boiling in the low quality region was dominant. Kandlikar"s correlation also showed the contribution of nuclear boiling. As the quality is increased, the contribution of convective evaporation was not significant. Lim"s correlation showed the highest heat transfer coefficient, and the contribution of nuclear boiling in the whole quality region was not as large as that of convective evaporation. Therefore, the total heat transfer surface area of the evaporator was the highest when obtained from Shah"s correlation. Low value was obtained when obtained from the correlation of Lim. In the condenser, the shell-side heat transfer coefficient obtained from Nusselt analysis was the lowest, followed by Kern and Eissenberg. The heat transfer surface area of the condenser showed the highest when obtained from Nusselt analysis.

Experimental study of the falling film evaporation coefficients of R290 in a horizontal enhanced tube array

In this study, the falling film evaporation heat transfers of R290 on an array composed of five enhancement horizontal tubes (groove tubes) are studied. The tests are performed at constant saturation temperatures 5.5 °C with change of heat flux from 10 to 40 kW/m2. The film Reynolds number ranges from 200 to 2200 and the film flow rate of refrigerant is between 100 and 660 kg/h.The results show that the film flow rate and heat flux have significant effects on R290 falling film evaporation heat transfer coefficients (HTCs) of the tubes in the tube array. With decreasing the film flow rate on the five tubes the tube HTCs display two stages, a plateau stage and a sharp drop stage. The heat transfer coefficients firstly keep more or less constant at the plateau stage and then decreasing rapidly. At the same nominal film Reynolds number the tube averaged heat transfer coefficients of tube No. 1 to tube No. 5 decrease in order of the increasing tube number from top to bottom of the array. The falling film evaporation HTC of R290 on single enhanced tube is about 4.5 times of single smooth tube HTC, and the HTCs of the enhanced tube array is higher than single smooth tube by more than 2.5 times. In addition, the R290 HTCs of the tube array are higher than those of R134a for the same tube array in the plateau region by about 25%. It is found that at high heat flux of 30–40 kW/m2, the heat transfer coefficient variation with film Reynolds number of the lower enhanced tubes in the tube array exhibits severe undulating characteristics.

PII: S0928-1258(20)30052-8

In this study, the falling film evaporation heat transfers of R290 on an array composed of five enhancement horizontal tubes (groove tubes) are studied. The tests are performed at constant saturation temperatures 5.5 °C with change of heat flux from 10 to 40 kW/m2. The film Reynolds number ranges from 200 to 2200 and the film flow rate of refrigerant is between 100 and 660 kg/h.The results show that the film flow rate and heat flux have significant effects on R290 falling film evaporation heat transfer coefficients (HTCs) of the tubes in the tube array. With decreasing the film flow rate on the five tubes the tube HTCs display two stages, a plateau stage and a sharp drop stage. The heat transfer coefficients firstly keep more or less constant at the plateau stage and then decreasing rapidly. At the same nominal film Reynolds number the tube averaged heat transfer coefficients of tube No. 1 to tube No. 5 decrease in order of the increasing tube number from top to bottom of the array. The falling film evaporation HTC of R290 on single enhanced tube is about 4.5 times of single smooth tube HTC, and the HTCs of the enhanced tube array is higher than single smooth tube by more than 2.5 times. In addition, the R290 HTCs of the tube array are higher than those of R134a for the same tube array in the plateau region by about 25%. It is found that at high heat flux of 30–40 kW/m2, the heat transfer coefficient variation with film Reynolds number of the lower enhanced tubes in the tube array exhibits severe undulating characteristics.

ДОСЛІДЖЕННЯ ВПЛИВУ ПОЛОЖЕННЯ ТРУБКИ В ПУЧКУ ТРУБ КОЖУХОТРУБЧАСТОГО ТЕПЛООБМІННИКА НА ПРОЦЕС ТЕПЛОВІДДАЧІ

The paper is concerned with an issue of liquid distribution in the diametrical bank tubes of the shell and tube heat exchanger. The experimental-theoretical approach for the research has been applied. The data on the determination of velocities of the heated liquid through the pipes of the heat exchanger have been obtained and processed. The research was carried out at the created experimental factory. Water at a temperature of 20 ºС has been supplied to the tubes. The temperature of the water has been maintained by a thermostat. The temperature at the outlet of the tube has been measured with a thermocouple element. Water (heat conductor,) at a temperature of 60, 80 or 95 ºС has been circulating in the outside of tubes space. The temperature of the water has been maintained by pumping it through a thermostat. The velocities of the heated liquid in the diametric bank tubes have been determined, which differed considerably depending on the position of the tube. Consequently, the results of the research obtained have discovered the significant deviations of such parameters as the liquid temperature at the outlet of the apparatus, tube wall temperature and heat transfer coefficients between the tube and heated liquid. The distribution insert has been used, in order to match the above-mentioned indicators. The distribution insert is a disk with the optimized holes. The alignment of the liquid velocities through the tubes of the diametric bank has been observed, which has consequently led to the uniform heating of both the central and side tubes. The study outcome has proven to be the solution to prevent the overheating of the peripheral tubes. Thus, the generation of a uniform field of velocities for the heat transfer agent through the tubes of the shell and tube heat exchanger contributes to the uniform heating of both central and peripheral tubes, and increases the heat transfer coefficient in the side tubes. The conclusion has been drawn that the reason for the failure or heat transfer low efficiency in the peripheral tubes of the shell and tube heat exchanger is the nonuniform distribution of liquid velocities in different tubes and as a consequence, the low heat transfer coefficient in those tubes where the velocity is low.

3D-printed tubes with complex internal fins for heat transfer enhancement—CFD analysis and performance evaluation

Additive manufacturing (AM), also known as 3D printing technology, is applied to fabricate complex fin structures for heat transfer enhancement at inner surface of tubes, which conventional manufacturing technology cannot make. This work considered rectangular fins, scale fins, and delta fins with staggered alignment at the inner wall of heat transfer tubes for heat transfer enhancement of internal flows. Laminar flow convective heat transfer at 500 < Re < 2000 has been numerically studied, and heat transfer performance of the tubes with 3D-printed interrupted fins has been compared to that with conventional straight continuous fins and smooth tubes. The benefit from heat transfer enhancement and the loss due to increased pumping pressure is evaluated using the total entropy generation rate in the control volume of heat transfer tube. The heat transfer coefficient in tubes with interrupted fins in staggered arrangement can have 2.6 times of that of smooth tube and 1.4 times of that with conventional continuous straight fins. The entropy generation in the tubes with interrupted fins in staggered arrangement only has 30–50% of that of smooth tube or tube with traditional continuous straight fins. The benefit of using interrupted fins in staggered arrangement is significant.

Pool boiling of horizontal mini-tubes in unconfined and confined columns

Pool boiling on confined and unconfined tube columns was investigated. A model to predict bulk void fraction in a confined tube column was developed and validated experimentally, returning a mean predictive accuracy error of 12.5%. A semi-empirical model was also developed from bubble plume images to evaluate bulk void fraction in an unconfined plume around a tube column. Within an unconfined plume, void fraction increases monotonically with column height, indicating that a column height exists beyond which the mean column heat transfer coefficient is adversely affected by dryness. Pool boiling experiments were undertaken in Novec 649 to investigate the effects of external confinement, tube spacing, and column height on heat transfer. Increasing the column height in a column showed an initial decline in power density to a constant at ∼30 MW m−3. A tube void fraction threshold was identified as changing the location of critical heat flux from the bottom tube to the top tube in a column, and to cause a deterioration in tube heat transfer coefficient at high heat fluxes.

Experimental Study Of R141b Flow Boiling Compact Evaporator in Organic Rankine Cycle for Waste Heat Recovery

Indonesia is one of country that has plenty geothermal energy resource. Because of the significant potential, the energy can be used as a power plant. Geothermal resource with low pressure and temperature can be used in Organic Rankine Cycle (ORC) technology. ORC is one of power plant system which can use waste energy by using organic working fluid or refrigerant that is able to evaporate at low pressures and temperatures . In this research, experimental of evaporator by using the organic Rankine cycle system from the gas stove heat source.The experimental study was conducted by experimenting of evaporator Compact Heat Exchanger continuous fin type. For know typical of heat transfer, evaluation proses make three region, subcooled, evaporation and superhaet. The prediction of the Two phase change flow pattern was observed in detail against the effect of heat flux and mass velocity variations by Chen and Shah Correlation. The phase change process occurs under pressure conditions P = 5 bar where the saturation temperature is 86.9 oCFrom the calculation and analysis, the maximum rate of heat transfer is 17.345 kW at 468 kg/m2s and heat flux 83 kW/m2. The evaporation process occurs at temperatures above 95 oC. Internal tube heat transfer coefficient of two-phase convection with consideration of the highest nucleate boiling and convective boiling of the evaporator was 2443.69 W/m2K in 234 kg/m2s mass flux refrigerant. Heat Flux with 1.94 kW/m2 heaten (Chen's Methode) and from the result of analysis proposed by Shah's Methode was obtained 1624.90 W/m2K in 468 kg/m2s mass flux refrigerant and 1.94 kW/m2 heat flux. the value of convection coefficient varies to the value of heat flux, mass flux and quality vapor

A study of the vortex-induced lateral vibration and heat transfer characteristics of elastic supported single tubes with different cross-sectional shapes

In this paper, the vortex-induced vibrational characteristics and heat transfer mechanisms of three tubes with different cross-sectional shapes are numerically studied. The results show that the characteristics of vortex-induced vibration of the vertical elliptical tube and circular tube are obvious. At low flow velocities, the vortex shedding force can affect the vibrational characteristics of horizontal elliptical tube, but the effect is not obvious with increasing flow velocity. When the frequency is locked, the vibrational amplitude of the vertical elliptical tube is the largest, followed in descending order by that of the circular tube, and that of the horizontal elliptical tube. The local heat transfer coefficients of tube at different vibration time are different. High local heat transfer coefficients are produced when vortices form on local walls or—when the relative velocity between the fluid and the heat transfer wall is relatively large. The effects of vortex-induced vibration enhancement heat transfer of these three kinds of tubes are different. The vertical elliptical tube can enhance the heat transfer by 28.6%, the circular tube can enhance it by 21.3%, and the horizontal elliptical tube can only enhance it by 3.7%.

A CFD modeling investigation for structure optimization of a rotary steam tube dryer

This paper presents an optimized structure to improve the performance of rotary steam tube dryer by assembling the so called ‘Y’ shape flights. A verified CFD model, which was developed and validated in the previous work, was employed to verify the optimized structure by the comparisons of concentration distribution, velocity distribution and heat transfer coefficient. The simulation results showed that assembling ‘Y’ shape flights in a rotary steam tube dryer is an effective approach to increase material filling ratio and heat exchanging area. The optimized construction is able to reduce the wear of the material to the tube surface, due to the low maximum particle velocity. The optimized structure yields a uniform particle velocity distribution and high average surface heat transfer coefficient of tubes which is about ten times of that without flights.

Condensation Heat Transfer and Pressure Drop of R-404A in 7.0 mm O.D. Smooth and Microfin Tube at Low Mass Fluxes

R-404A condensation heat transfer and pressure drop data are provided for 7.0[Formula: see text]mm O.D. smooth and microfin tubes. Tests were conducted for a range of mass fluxes (from 80 to 200[Formula: see text]kg/m2s) and quality (from 0.2 to 0.8). The heat flux was 6[Formula: see text]kW/m2 and saturation temperature was 45[Formula: see text]C. It was found that both the heat transfer enhancement factor and the pressure drop penalty factor increase as mass flux increases. The range of pressure drop penalty factor (0.99–1.27) was smaller than that of heat transfer enhancement factor (1.21–1.96). Smooth tube heat transfer coefficients and pressure drops are reasonably predicted by Shah [An improved and extended general correlation for heat transfer during condensation in plain tubes, Int. J. HVAC&amp;R Res. 15 (2009) 889–913] and Jung and Radermacher [Prediction of pressure drop during horizontal annular flow boiling of pure and mixed refrigerants, Int. J. Heat Mass Transfer 32 (1989) 2435–2446] correlation, respectively. For the microfin tube, however, all the existing correlations do not adequately predict the present data. Poor predictions may be attributed to the lack of R-404A and low mass flux data in their database.

Heat transfer from immersed tubes in a pulsating fluidized bed

Heat transfer through immersed tubes in pulsating fluidized beds was investigated computationally using an Eulerian-Eulerian approach. The effects of pulsating frequency and configuration of the immersed tubes were studied. At low pulsating frequency, more orderly bubbling behaviors were observed and these gave rise to more uniform heat transfer rates from all tubes. An interesting heat transfer behavior whereby the heat transfer coefficient distribution around an immersed tube alternated between a needle-like and a wide fan-shaped pattern was observed for the first time in this study. An increase in pulsating frequency caused the fluidized bed to exhibit fluctuating heat transfer rates. The staggered tube configuration considered in this study was observed to aid in the development of more orderly bubbling behaviors, with heat transfer coefficient of tubes in the bottom row exhibiting similar oscillation amplitudes.

Heat transfer challenge and design evaluation for a multi-stage temperature swing adsorption process

Functionalized solid amine-based temperature swing adsorption (TSA) processes have recently been proposed as a potential way to reduce the energy-penalty of post-combustion carbon capture processes. Thereby, multi-stage fluidized bed contactors with immersed heat exchanger surfaces and counter-current flow of solids and gas phase may solve the heat transfer challenge while maintaining the thermodynamic process requirements. Hence, the present work develops design requirements for TSA stages based on achievable heat transfer rates in bubbling fluidized beds. The considered particles are Geldart Type B. It is shown that the pressure drop of multi-stage fluidized bed TSA units for flue gas CO2 capture is practically determined by the heat exchange requirement. Scalability, maintainability and durability of different heat exchanger geometries are considered. The net movement and mixing of particles within the bubbling bed stage must be maintained in spite of the immersed heat exchangers concerning possible dead zones in the area of the tube bundles. Comprehensive models are used to predict heat transfer coefficients for tubes immersed in fluidization. A heat transfer measurement test device for optimization of the heat exchanger geometry has been put into operation and heat exchange measurement results are compared to calculated heat transfer coefficients. It is shown that experimentally obtained heat transfer rates for single tubes are in good agreement with modeled values. A model proposed for Geldart A particles is used to estimate heat transfer rates for two particular tube bundles with a tube diameter of 25mm and horizontal tube spacing of 2.2 and 2.8. It is shown that the calculated results represent heat transfer rates qualitatively and quantitatively for tube bundle heat exchangers immersed in Geldart Type B particle fluidized beds. Although this article has been motivated by heat exchange in TSA, it may be of interest for other applications concerned with heat transfer between bubbling fluidized beds and immersed heat exchanger surfaces.

Convective boiling of R-134a on enhanced-tube bundles

The current paper presents the experimental investigation of the heat transfer performance and effect of tube pitch on highly enhanced surface tube bundles. The fluid–tube combination used was R-134a and the enhanced tube TBIIHP. Three pitch-to-diameter ratios were studied: 1.167, 1.33, and 1.5; all with a staggered triangle arrangement. Twenty enhanced tubes were used in each bundle; the tube outer diameter and length are 19.05 mm (3/4 inch) and 1 m (39.36 inch), respectively. Three input variables were investigated: heat flux (5–60 kW/m2), mass flux (15–55 kg/m2.s), and quality (10–70%). The test saturation temperature was 4.44 °C. A local method employing the EBHT technique was implemented in data reduction. All tube bundles showed strong dependency on heat flux. The smallest P/D bundle showed a considerably lower performance than the other two. When compared to the pool boiling performance, the smallest P/D bundle was lower while the other two showed a closer performance. The P/D 1.33 bundle outperforms P/D 1.167 bundle and provide quite similar performance to the P/D 1.5. When considering the refrigerant quantity, the P/D 1.5 bundle uses more refrigerant compared to the P/D 1.33; the latter proves to be the optimum. Finally, a new enhanced tube heat transfer coefficient bundle model was proposed based on the extensive data collected and the studied bundle phenomena.

Numerical Study on Local Flow Field and Temperature Field of Helical Baffles Heat Exchanger

Models of continuous helical baffles and quarter helical baffles heat exchangers are established. With large CFD analysis software FLUENT, the distribution characteristics of local flow field and temperature field of helical baffles heat exchangers are investigated through numerical simulation. And comprehensive performances of both heat exchangers are compared and studied with entransy dissipation. The results show:In the research of heat exchanger, the evaluation standard of entransy dissipation is consistent with that of comprehensive performances. When the flow of shell side is the same, the entransy dissipation value of continuous helical baffles heat exchanger is less than that of quarter helical baffles heat exchanger. The distribution characteristics of local flow field and temperature field of both heat exchangers present the same rules, in the central part of shell side, heat transfer coefficient of tubes is the highest. Along the radial direction, both helical flow and heat transfer coefficient of tubes first increase then decrease. Compared to continuous baffles, the discontinuity of baffles could enhance local heat transfer. Yet, when flow increases to an extent, the local heat transfer in the center will be weakened. The results provide theoretical basis for the improvement of structure forms of helical baffles.