Shell-side Heat Transfer Coefficient Research Articles

Global optimization for the design of shell and tube horizontal thermosyphon reboiler

Shell and tube horizontal thermosyphon reboilers (STHTs) find wide applications in the process industry particularly due to their inherent advantages in handling large duties, high viscosity fluids and low fouled susceptibility. However, current design commercial packages suffer from obvious limitations including extensive user manipulations, trial-and-error necessity, increased human factor influence. To overcome these limitations, we develop in this work a rigorous MINLP model for STHT sizing, by achieving automated selection of detailed exchanger geometries with optimal overall heat transfer coefficient. The corrected minimum cross-flow area in shell-side is incorporated to accommodate full cross-flow patterns in tube bundle, thus handling popular service of X shell without baffle construction. A dependable convective boiling heat transfer model is proposed to obtain the shell-side heat transfer coefficient, validated with Aspen EDR. The critical variable, heat flux, which affects nucleate boiling heat transfer performance, is optimized through a simultaneous equation-solving process using a global solver, reducing excessive unit overdesign. Pressure balance between STHT and distillation column is fully considered by a proposed optimization model incorporating pressure drop and pipe sizing. By employing global optimization techniques and automating the design process, this innovative approach minimizes manual adjustments and provides more accurate and cost-effective designs.

An investigation on structural parameters optimization and coupled heat transfer of LNG submerged combustion vaporizer

Submerged combustion vaporizer (SCV) owns an extremely efficient multiphase heat exchanger adopted in the coastal liquefied natural gas (LNG) receiving terminal. Overall vaporization efficiency of SCV mostly depends on the matching relationship of structural parameters and coupled heat transfer characteristics, which has been rarely addressed in previous studies. In the present work, an integrated SCV experimental platform with handling capacity of 50 kg/h was set up to validate the reliability of numerical model and method. Additionally, on account of multi-parameter orthogonal combination optimization method, the effects and sensitivity orders of structural parameters (transverse tube pitch, longitudinal tube pitch, orifice size and number of distributor branch) on dynamics performance of SCV were investigated. Finally, the coupled heat transfer between gas–liquid two-phase flow and supercritical LNG gasification was revealed in view of optimized parameters. Results indicated that the transient numerical tube-side outlet temperature could be consistent with experimental data. For the shell-side heat transfer coefficient, the sensitivity order was transverse tube pitch > orifice size > longitudinal tube pitch > number of distributor branch. Nevertheless, for the shell-side pressure drop, the sensitivity order was longitudinal tube pitch > transverse tube pitch > orifice size > number of distributor branch. Under the condition of optimization scheme, the heat provided by gas–liquid two-phase flow could meet the requirements of supercritical LNG gasification, the NG outlet temperature might achieve approximately 272 K. The present outcomes could lay a foundation for the optimization design and deep understanding for actual SCV facility.

Tube bundle evaporators with LGWP refrigerant R1234ze(E)

With new low-GWP HFO refrigerants, the heat transfer performances and methods for decreasing system refrigerant inventory are receiving increasing interest. In shell-and-tube heat exchangers, refrigerant distribution via pressurized liquid spray has the potential for high heat transfer performance while reducing refrigerant charge. However, no published studies have investigated LGWP refrigerants with spray evaporation on tube bundles. A test apparatus was constructed to measure the shell-side heat transfer coefficients of R1234ze(E) on bundles of tubes with two different enhanced-surface types and in two different bundle geometries at various refrigerant saturation temperatures. The results showed strong dependence on refrigerant properties, tube heat flux, enhanced-surface type, bundle geometry, and refrigerant inlet subcooling. The bundle heat transfer coefficients of R1234ze(E) were similar to that of R134a in the same test setup, usually within ±15% for similar conditions. In both cases, they first increased with the heat flux until a local maximum value was achieved. A localized dryout of the tubes at the bottom of the bundle penalized the overall bundle heat transfer coefficient at very high heat flux. For the condensing surface, bundle heat transfer coefficients rarely exceeded 10 kW/m2-K, whereas values in excess of 30 kW/m2-K were sometimes seen for the evaporating surface.

Flow Characteristics and Heat Transfer Performances of Quadrant Helical Baffle Heat Exchanger with Grooved Joint

Helical baffle heat exchanger has a wide application in many industrial fields because of its high efficiency and low resistance. A new structure of the grooved helical baffle is proposed to strengthen the stability between the overlapped baffles during the spiral flow of fluid. Based on this structure, the liquid water was selected as the working medium in the tube side and shell side, the flow field characteristics and heat transfer performances of the quadrant helical baffle heat exchanger are numerically analyzed using software FLUENT 2017. The results show that when the helical angle is large (50°) and the overlapped amount is small (0.5), the comprehensive performance of the heat exchanger is the best. Therefore, the heat exchanger performance can be improved by choosing the appropriate combination of helical angle and overlapped amount. The correlation formula of the shell side heat transfer coefficient with helical angle, overlapped amount and mass flow rate is obtained by means of regression analysis, which can provide a reference for engineering application and optimal design of grooved helical baffle heat exchanger.

Development of improved correlations for shell side heat transfer co-efficient in multi-tubular reactors network heat exchanger

The multi-tubular reactor takes the form of a shell and tube heat exchanger. The baffles that became of interest were the disk and doughnut baffles as they provided a 15 % greater effectiveness than the commonly used segmental baffle. The shell side heat transfer coefficient is usually predicted by correlations developed by Donohue (1949) and Goyal & Gupta (1984) for disk and doughnut baffles. However, these correlations result in inaccuracies due to the complexity of the configuration. Therefore, Slipcevic (1978), had developed a new method to calculate the shell side heat transfer coefficient. The Slipcevic method takes into consideration the annular flow, the crossflow and the doughnut flow. However, certain portions were gone unconsidered by this method. Therefore, the aim of this study was to modify the Slipcevic method to generate a more accurate shell side heat transfer coefficient. The heat transfer coefficient calculated using the original Slipcevic method was determined to be 58.6 W/m^2. K. The modified method resulted in a coefficient of 49.9 W/m^2. K. The modification resulted in a coefficient 14.8 % less than the original method. Since the simulated value for the propylene process was 15.8 % lower than the Slipcevic procedure, this revealed that the modification was slightly more accurate. The difference of 6.5 % between the two percent differences may be due to inaccuracies resulting from the assumptions of triangular gaps and that the wall viscosities were equivalent to the bulk viscosities.

Numerical analysis of thermal performance of waste heat recovery shell and tube heat exchangers on counter-flow with different tube configurations

This study investigates the effect of tube layout configurations on the hydraulic-thermal performance of shell-and-tube heat exchangers (STHXs) as waste heat recovery systems. The STHXs are triangular (30°, STHX-T), rotated triangular (60°, STHX-RT), and combined (STHX-C). Water at a temperature of 10 °C was circulated through a bundle of tubes inlet to recover waste heat from hot water at the temperature of 65 °C. Water was circulated through the shell inlet within the mass flow rate range of 0.5 ≤ ṁ ≤ 3.5 kg/s. ANSYS-Fluent was used to perform a three-dimensional computational study under steady-state conditions. The turbulence model, realizable k-epsilon, was adopted because of the possible transition from laminar to turbulence. The results were validated with the Kern correlation for shell-side heat transfer coefficient and pressure drop. The temperatures, pressure drop, velocity, and overall heat transfer coefficient for all the cases were compared. Temperature contours, pressure contour, velocity vector, and velocity contour were presented for flow visualization. When the simulation results of the different STHXs were compared, the results revealed that the STHX-T layout has the highest overall heat transfer coefficient of 2307.09 W/m2K. The maximum pressure drop of 242.42 Pa, highest temperature drop in the shell zone of 4.48 K, and highest temperature rise in the tube side of 6.67 K, followed by STHX-C and STHX-RT layout were obtained.

Experimental investigation on heat transfer performances in half-cylindrical shell space of different heat exchangers

The superheated steam cooling section and the condensate cooling section of the power plant feedwater heaters and the countercurrent U-tube heat exchangers all involve heat transfer in half-cylindrical shell space. The overall and shell-side heat transfer coefficients (h.t.cs.), pressure drop, and the comprehensive performances of some half-cylindrical space heat exchangers with different baffle structures were experimentally investigated. The investigated structures include three ladder helical baffle types [single inclined ladder helical (SH), dual inclined ladder helical (DH) and folded ladder helical (FH)], three orifice baffle types [fillet triangle orifice (F), trefoil-orifice (T) and quatrefoil-orifice (Q)], and segmental baffles (S), and all schemes are of two baffle pitches. Under the same baffle pitch and working condition, the experimental results show that the shell-side h.t.cs. of the ladder helical baffle schemes are higher than those of the orifice baffle schemes and segmental baffle ones; and the shell-side pressure drops of the orifice baffle schemes are much lower than those of the ladder helical baffle schemes and the segmental ones. The values of average comprehensive index hoΔpo−1/3 of the ladder helical schemes FH-40, DH-40 and the orifice baffle schemes F-40 and T-40 are respectively 14.26%, 17.58%, 15.62% and 12.82% higher than that of the segmental scheme S-40.

Experimental study on heat transfer in a model of submerged combustion vaporizer

• Heat transfer experiment of submerged combustion vaporizer (SCV) model is conducted. • The shell-side, tube-side and overall heat transfer coefficients are obtained. • The average of shell-side heat transfer coefficient is about 300 W/(m 2 ·°C). • Two simple empirical correlations are developed for the overall tube-side heat transfer. The submerged combustion vaporizer (SCV) is widely used in the peak shaving of liquefied natural gas (LNG) supply. It is believed that SCV will have a great application prospect with the implementation of the peak-shaving policy of natural gas in China. SCV injects the flue gas after combustion directly into the water bath from its bottom, causing gas disturbance and two-phase flow in the water bath. The shell-side flow and heat transfer become unclear because of the gas disturbance. There is a lack of relevant theoretical basis in this regard. In order to master the operation mechanism of SCV, an experimental research is carried out on a SCV model which has the same structure and function as the actual small-size SCV. The shell-side, tube-side and overall heat transfer coefficients are obtained, and the influences of operation parameters on the heat transfer are investigated. The results indicate that in the range of the experimental parameters, the shell-side heat transfer coefficient is almost not affected by the frontal gas velocity and Reynolds number of the flue gas at orifices, and the average value is about 300 W/(m 2 ·°C). Meanwhile, the higher the flow rate and pressure of the tube-side medium, the greater the overall heat transfer coefficient. In addition, it is observed that if the gas disturbance stops, the heat transfer deterioration will occur. Finally, two simple empirical correlations are developed for the overall tube-side heat transfer. This study provides support for the design and application of SCV.

Experimental study and comparative performance analysis on thermal-hydraulic characteristic of a novel longitudinal flow oil cooler

The longitudinal flow heat exchanger possesses lots of merits but it exhibits poor heat transfer coefficient at low Re condition, which makes it difficult to be applied in the high viscosity fluid area. In this paper, a heat transfer augment solution for lubricating oil flowing on shell side of a novel longitudinal flow twisted trifoliate tube oil cooler was proposed. Experiments were conducted to comparatively investigate the thermal–hydraulic performance of a twisted trifoliate tube oil cooler and a conventional segmental baffle oil cooler. The tube side study demonstrates that the Nu and f of the twisted trifoliate tube are 17.5–75.8% and 16.9–62.9% larger than that of the smooth circular tube. The shell side study shows that at the same oil mass flow rate, the shell side heat transfer coefficient of the twisted trifoliate tube oil cooler is 66.3–148.9% higher than that of the conventional segmental baffle oil cooler with pressure drop increased by 31.6–65.2%. Furthermore, the shell side performance evaluation criterion h/ΔP of the twisted trifoliate tube oil cooler is 1.46 times larger than that of the conventional segmental baffle oil cooler on average. The possible mechanisms responsible for the heat transfer enhancement are analyzed. In addition, the predictive correlations of tube side and shell side of the twisted trifoliate tube bundles for Nu and f are deduced based on the experimental data. Results from current research could provide useful correlations and beneficial guidance for design and application of the longitudinal flow heat exchanger in low Re ranging of 40–250.

Colburn vs Bell Delaware approach for evaluation of thermohydraulic performance of a shell and tube heat exchanger: A theoretical study

STHX have assumed importance over the years due to its great versatility. Thermal and hydraulic characteristics dictate the performance of the heat exchanger. These factors are dependent on the inlet conditions, flow conditions, tube and shell geometry. Present paper presents a theoretical approach involved in calculating the thermohydraulic performance of a STHX using two methods- Colburn and Bell Delaware. Temperature of water on the hot side was varied- 50 °C, 70 °C and 90 °C and the cold fluid has been set to 30 °C. Plots of performance parameters such as heat load, shell side heat transfer coefficient, and effectiveness by both approaches have been discussed. From the results it can be concluded that the Bell Delaware is more reliable for calculation in practical scenarios as the losses that may occur are taken into consideration.

Numerical performance analysis of a novel shell-and-tube oil cooler with wire-wound and crescent baffles

Shell-and-tube oil coolers (STOC) are widely used in heat transfer of power systems. However, high-viscosity lubricants cause their oil-side heat transfer coefficients to be one order for magnitude lower than their water-side counterparts. Given this, a STOC with wire-wound (STOC-W) was designed to enhance the heat transfer of the oil cooler shell-side. The thermo-hydraulic performance of STOC-W is investigated by the numericalsimulation. According to the numerical calculation results of STOC-W, the STOC with wire-wound and crescent baffles (STOC-W-CB) was further proposed. The three factors (wire-winding angle, winding section shape, and baffles angle) that affect the heat transfer coefficient (HTC) of the STOC-W-CB were furtherly simulated and analyzed. The thermo-hydraulic performance of the STOC-W-CB and STOC with helical baffles (STOC-HB) were also compared. The results show that the structure of wire-wound and crescent baffles can effectively improve the shell-side heat transfer of the oil cooler. When Re is 201, the Performance Evaluation Criteria (PEC) of the STOC-W-CB is 2.2 times that of the bare tube cooler. The shell-side heat transfer coefficient of the STOC-W-CB are dramatically decreased with the increasing of the wire-winding angle. The best combination of the novel oil cooler is 30°-square wire winding with 10°-crescent baffles. When the Reynolds number is in the range of 100–350, the average heat transfer coefficient of STOC-W-CB is about 44% higher than that of STOC-HB.

Numerical simulation of the effect of baffle cut and baffle spacing on shell side heat exchanger performance using CFD

Abstract Heat exchangers possess a significant role in energy transmission and energy generation in most industries. In this work, a three-dimensional simulation has been carried out of a shell and tube heat exchanger (STHX) consisting of segmental baffles. The investigation involves using the commercial code of ANSYS CFX, which incorporates the modeling, meshing, and usage of the Finite Element Method to yield numerical results. Much work is available in the literature regarding the effect of baffle cut and baffle spacing as two different entities, but some uncertainty pertains when we discuss the combination of these two parameters. This study aims to find an appropriate mix of baffle cut and baffle spacing for the efficient functioning of a shell and tube heat exchanger. Two parameters are tested: the baffle cuts at 30, 35, 40% of the shell-inside diameter, and the baffle spacing’s to fit 6,8,10 baffles within the heat exchanger. The numerical results showed the role of the studied parameters on the shell side heat transfer coefficient and the pressure drop in the shell and tube heat exchanger. The investigation shows an increase in the shell side heat transfer coefficient of 13.13% when going from 6 to 8 baffle configuration and a 23.10% acclivity for the change of six baffles to 10, for a specific baffle cut. Evidence also shows a rise in the pressure drop with an increase in the baffle spacing from the ranges of 44–46.79%, which can be controlled by managing the baffle cut provided.

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.

Investigation of the thermal-hydraulic characteristics in the shell side of heat exchanger with quatrefoil perforated plate

Quatrefoil perforated plate (QPP) is a kind of whole circular support plate for the shell side of shell-and-tube heat exchanger (STHX), and the design and optimization of heat exchanger with this support structure are the key technologies to study and improve the performance of heat exchanger. The influences of the hole height and plate spacing of the QPP on the thermal-hydraulic performance of the heat exchanger were studied mainly by using computational fluid dynamics (CFD) method. And the reliability and accuracy of the numerical results were verified by compared with experimental results. With Reynolds number varying from 5000 to 20,000, the results show that the heat transfer coefficient and pressure drop in the shell side of the heat exchanger both increase with the decrease of the hole height and the plate spacing of the QPP, but the shell side heat transfer coefficient per unit pressure drop h/Δp decreases. Under the conditions of the same fluid flow rate and same plate spacing, compared with segmental baffle heat exchanger, the comprehensive performance h/Δp of heat exchanger with QPPs is improved by 27%–41%. The empirical correlations for Nusselt number and pressure drop in the shell side of heat exchanger with QPPs were obtained and the calculation deviation of correlations both are within ±10%, which can be used to guide engineering design and practice.

Numerical and Experimental Investigation on Performance of Convex-Cut Baffles in Shell-and-Tube Heat Exchanger

In this study, comparative performance of single-segmental baffle and a newly developed baffle – convex-cut in shell-and-tube heat exchanger were both numerically and experimentally investigated. For the numerical analysis, three working fluids (engine oil, water and air) were successively utilised on the shell-side of heat exchangers with 30, 35, 40 and 45% convex-cut (CeC_STHE) and 25% segmental (SS_STHE) baffles, and the resulting models were solved in COMSOL Multiphysics. Experiments were carried out on 30% CeC_STHE and SS_STHE exclusively running on water. The data obtained were used to determine the weighted shell-side heat transfer coefficient and weighted performance factor of each heat exchanger. Hence, the results for all the ranges of Reynolds number indicate that the shell-side heat transfer coefficients of all the CeC_STHEs are lower than that of SS_STHE except for the 30% CeC_STHE. However, the SS_STHE showed greater pressure drop than the CeC_STHEs. The choice of working fluid had more influenced on the weighted shell-side heat transfer coefficient CeC_STHE. Moreover, the weighted performance factors of the CeC_STHEs indicated positive values. Thus, 30% CeC_STHE demonstrated a better performance while the 45% had the lowest performance.

Investigation on shell side performance in half-cylindrical desuperheating zone of ladder type helical baffle heat exchangers

The shell-side flow and heat transfer performance in half-cylindrical desuperheating zones of high pressure feedwater heaters were simulated by Fluent. The investigated structures include three ladder type helical baffle heat exchangers, i.e. the two unilateral ladder types with folded and inclined plane strip baffles, and the bilateral plane type, and two comparative schemes of eggcrate support type and double-segmental type and all baffle types are of three different baffle pitches. The visualized flow patterns in the desuperheating zone were demonstrated on special slices to clearly reveal the mechanisms and impacts of baffle configurations and geometrical parameters on thermal-hydraulic performances. The numerical results show that the shell-side heat transfer coefficients ho of all ladder type helical models are superior to those of both eggcrate support and double-segmental ones, among which the bilateral plane model has the best performances. The average values of ho and evaluation indexes hoΔpo−1 and hoΔpo−1/3 of nine helical models raise 2.99%, 149.50% and 36.26% respectively in contrast to those of the corresponding double-segmental models, and the average values of evaluation performance η for schemes of three baffle pitches 80, 120 and 160 (mm) are respectively 1.202, 1.367 and 1.525.

Experimental investigation of the condensation mechanisms in the shell side of spiral wound heat exchangers

An experimental investigation of the water vapor condensation mechanisms occurring in the shell side of spiral wound heat exchangers was conducted. Eight different test sections with varying structures were fabricated, each with an observation window, to investigate the effects of the geometric parameters on the condensation process. The experimental results indicated that there is a minimum condensation heat transfer coefficient for the top tube as the inclination of tube increases because of the changes in the film thickness. A comparison of the heat transfer coefficient between each individual tube and the entire test section was conducted and indicated that the heat transfer in the lower tubes dominate the overall heat transfer of the test section. While increases in the tube pitch changes the velocity field in the shell side, it also results in a decrease in the shell-side condensation heat transfer coefficient and the overall heat transfer of the test section.

Experimental investigation on shell-side performance of a novel shell and tube oil cooler with twisted oval tubes

The lubrication oil cooler is widely used in many industries. The lubrication oil is usually operated in a laminar state with Reynolds number less than 1000 due to its high viscosity characteristic. It is hard to augment the heat transfer performance of high viscosity fluids without obvious pressure drop. A lot of researches have been conducted on the shell-side heat transfer and fluid flow characteristics of twisted oval tube heat exchangers. However, the previous study mainly focused on the high Reynolds number regime and the correlations obtained are not suitable for low Reynolds flow. In the present paper, a novel self-supported shell-and-tube oil cooler with twisted oval tube bundles (OCTT) is designed. Experiments are conducted to investigate the shell-side heat transfer and pressure drop of OCTT compared to the conventional shell-and-tube oil cooler with round tube bundles (OCRT) in low Reynolds number flow. The experimental results indicate that at identical oil volume flow rate, the shell-side pressure drop of OCTT is lower than that of OCRT. Furthermore the shell-side heat transfer coefficient per unit pressure drop of OCTT is larger than OCRT. The empirical equations for Nusselt number and friction coefficient of OCTT in low Reynolds number ranging of 50–600 are also deduced from the experimental data, which could provide a beneficial guidance for the design of OCTT.

Experimental Investigation of Shell-Side Performance and Optimal Design of Shell-and-Tube Heat Exchanger with Different Flower Baffles

A novel structure for a shell-and-tube heat exchanger (STHX) with triple-layer flower baffles consisting of three blades is proposed in this article. This study also compares the performance of three heat exchangers with triple-layer flower baffles, double-layer flower baffles, and segmental baffles. In order to compare the hydrodynamics and heat transfer characteristics of the three heat exchangers, a water–water heat transfer experiment is designed. The experiment is carried out in a counter-current flow pattern with hot water in the shell and cold water in the tube. Based on the experimental data, at the same flow rate, the shell-side heat transfer coefficients of the STHXs with triple-layer flower baffles and double-layer flower baffles are 31.7% and 14.3% higher than those of traditional segmental baffles, respectively. With an increased number of blades, the STHX with triple-layer flower baffles achieves a comprehensive performance that is 23.7% improved over the STHX with double-layer flower baffles. Finally, an experimental correlative formula is fitted for the heat exchanger with flower baffles and an optimal design scheme for shell-side heat transfer enhancement is proposed.

Thermal-hydraulic analysis of water based ZrO2 nanofluids in segmental baffled shell and tube heat exchangers

Thermal-hydraulic characteristics of water based ZrO2 nanofluids has been investigated in a segmental baffled shell and tube heat exchanger in turbulent flow regime. The effect of Reynolds number, nanoparticle loading, mass-flow rate, and tube lay-out has been analysed on overall heat transfer coefficient. The effect of Reynolds number on the tube side pressure drop and convective heat coefficient have also been discussed. The effect of shell side mass-flow rate was also investigated on shell side heat transfer coefficient determined using Bell-Delaware method. The nanoparticle volume concentration is taken very low i. e. 0.2%, 0.4%, and 0.8%, respectively. The improvement in both tube side convective heat transfer coefficient and overall heat transfer coefficient has been observed. The maximum improvement in the convective heat transfer coefficient is found to be 14.1% for 0.8% ZrO2 nanofluids. However, the percentage enhancement in tube side pressure drop was higher than the percentage increment in the tube side heat transfer coefficient.