Shell-side Heat Transfer Coefficient Research Articles

Experimental Study of the LASH Baffle Heat Exchanger With Arc-Tangent Corrugated Tubes

In this paper, fluid flow and heat transfer of fluid flow in the shell-side of the large-and-small-hole (LASH) baffle heat exchangers with the arc-tangent corrugated (ATC) tubes are experimentally studied and compared with the conventional segmental baffle heat exchangers. It is founded that the shell-side baffle pressure drops for the LASH baffle heat exchangers with ATC tubes are greatly decreased. Although the fluid in the shell-side flowing in a form of parallel jet, the shell-side pressure drops with the LASH baffles, and the ATC tubes are also proportional to the square of the flow rate. Using ATC tubes can significantly raise the shell-side heat transfer coefficients of the heat exchangers. For the comprehensive evaluation, α s /Δp s of the heat exchanger with LASH baffles and ATC tubes could be 4.35 times of that of the heat exchanger with 25% cut away segmental baffle and the smooth tubes.

Multi-objective optimization of shell and tube heat exchangers

The effectiveness and cost are two important parameters in heat exchanger design. The total cost includes the capital investment for equipment (heat exchanger surface area) and operating cost (for energy expenditures related to pumping). Tube arrangement, tube diameter, tube pitch ratio, tube length, tube number, baffle spacing ratio as well as baffle cut ratio were considered as seven design parameters. For optimal design of a shell and tube heat exchanger, it was first thermally modeled using ε–NTU method while Bell–Delaware procedure was applied to estimate its shell side heat transfer coefficient and pressure drop. Fast and elitist non-dominated sorting genetic algorithm (NSGA-II) with continuous and discrete variables were applied to obtain the maximum effectiveness (heat recovery) and the minimum total cost as two objective functions. The results of optimal designs were a set of multiple optimum solutions, called ‘Pareto optimal solutions’. The sensitivity analysis of change in optimum effectiveness and total cost with change in design parameters of the shell and tube heat exchanger was also performed and the results are reported.

Experimental study of mixed convection heat transfer in vertical helically coiled tube heat exchangers

Abstract In this study the mixed convection heat transfer in a coil-in-shell heat exchanger for various Reynolds numbers, various tube-to-coil diameter ratios and different dimensionless coil pitch was experimentally investigated. The experiments were conducted for both laminar and turbulent flow inside coil. Effects of coil pitch and tube diameters on shell-side heat transfer coefficient of the heat exchanger were studied. Different characteristic lengths were used in various Nusselt number calculations to determine which length best fits the data and several equations were proposed. The particular difference in this study in comparison with the other similar studies was the boundary conditions for the helical coils. The results indicate that the equivalent diameter of shell is the best characteristic length.

Laminar forced convection heat transfer in helical coiled tube heat exchangers

A numerical investigation of the forced convection heat transfer from vertical helical coiled tubes at various Reynolds numbers, various coil-to-tube radius ratios and non-dimensional coil pitch was studied. The particular difference in this study compared to other similar studies is the boundary conditions for the helical coil. Most studies focus on constant wall temperature or constant heat flux, whereas in this study it was a fluid-to-fluid heat exchanger. The purpose of this article is to assess the influence of the tube diameter, coil pitch and shell-side mass flow rate over the performance coefficient and on shell-side heat transfer coefficient of the heat exchanger. Different characteristic lengths were used in the Nusselt number calculations to determine which length best fits the data. It was deduced that tube diameter was best choice for the characteristic length.

Bundle effect of ammonia/lubricant mixture boiling on a horizontal bundle with enhanced tubing and inlet quality

Shell-side heat transfer coefficients of individual tubes for ammonia/lubricant mixture boiling on a 3 × 5 enhanced tube bundle were measured, enabling a detailed study of tube bundle effect under the influences of inlet quality, concentration of miscible lubricant (co-polymer of polyalkylene glycol, PAG), saturation temperature, and heat flux. Tests were conducted in the range of heat flux from 3.2 to 32.0 kW/m 2, simulated inlet quality from 0.0 to 0.4, saturation temperature from −13.2 to +7.2 °C, and lubricant concentration from 0 to 10%. The data show that bundle effect is more significant at a higher saturation temperature. Most of the data in the bottom row are lower than the single-tube heat transfer coefficient data at a low saturation temperature. Lubricant renders the heat transfer coefficient lower in lower rows and higher in higher rows, therefore a larger range of data variation.

Experimental Study of Shell-Side Heat Transfer Coefficient and Pressure Drop for an Integrally Helical Baffled Heat Exchanger Combined with Different Enhanced Tubes

Experiments were performed to compare the shell-side heat transfer coefficient and pressure drop of an integrally helical baffle heat exchanger with rib-shaped fin tubes to those of that with low-fin tubes for oil cooling using water as a coolant. The experimental results showed that for the heat exchanger with rib-shaped fin tubes, the shell-side Nusselt and Euler numbers were augmented by 90−130% and 10%, respectively. The increase in heat transfer is significantly greater than that in pressure drop for rib-shaped fin tubes. Correlations have been suggested for both the shell-side Nusselt and Euler numbers for the two heat exchangers with different tube types and give very good agreement with experimental results. It is a promising route to use rib-shaped fin tubes instead of low-fin tubes for improving the performance of an integrally helical baffle heat exchanger.

Enhancing the heat transfer performance of triangular-pitch shell-and-tube evaporators using an interior spray technique

In spray type evaporators using a conventional overhead spray method, a dry-out phenomenon occurs on the lower surface of the evaporator tubes under high surface heat flux conditions, and thus the heat transfer performance of the evaporator system is seriously impaired. This study shows that in a compact triangular-pitch shell-and-tube evaporator, the dry-out problem can be delayed through the use of an interior spray method, in which each heater tube within the bundle is sprayed simultaneously by two nozzles. The experimental results reveal that the shell-side heat transfer coefficients obtained using the proposed spray technique are significantly higher than those achieved in a conventional flooded type evaporator. The results also show that the heat transfer performance improves as the saturation temperature decreases since the density and thermal conductivity of the sprayed liquid increase. Finally, it is shown that for a constant heat flux and saturation temperature, the heat transfer coefficient increases with an increasing refrigerant mass flow rate.

An experimental investigation of heat transfer enhancement for a shell-and-tube heat exchanger

For the purpose of heat transfer enhancement, the configuration of a shell-and-tube heat exchanger was improved through the installation of sealers in the shell-side. The gaps between the baffle plates and shell is blocked by the sealers, which effectively decreases the short-circuit flow in the shell-side. The results of heat transfer experiments show that the shell-side heat transfer coefficient of the improved heat exchanger increased by 18.2–25.5%, the overall coefficient of heat transfer increased by 15.6–19.7%, and the exergy efficiency increased by 12.9–14.1%. Pressure losses increased by 44.6–48.8% with the sealer installation, but the increment of required pump power can be neglected compared with the increment of heat flux. The heat transfer performance of the improved heat exchanger is intensified, which is an obvious benefit to the optimizing of heat exchanger design for energy conservation.

Improved Prediction of Shell Side Heat Transfer in Horizontal Evaporative Shell and Tube Heat Exchangers

This paper presents an improved prediction method for the heat transfer and pressure drop in the shell side of a horizontal shell and tube evaporator. The results from an experimental test program are used in which a wide range of evaporating two-phase shell side flow data was collected from a TEMA E-shell evaporator. The data are compared with shell side heat transfer coefficient and pressure drop models for homogeneous and stratified flow. The comparison suggests a deterioration in the heat transfer data at low mass fluxes consistent with a transition from homogeneous to stratified flow. The pressure drop data suggest a stratified flow across the full test range. A new model is presented that suggests the transition in the heat transfer data may be due to the extent of tube wetting in the upper tube bundle. The new model, which also takes into account the orientation of the shell side baffles, provides a vast improvement on the predictions of a homogenous type model. The new model would enable designers of shell side evaporators/reboilers to avoid operating conditions where poor heat transfer could be expected, and it would also enable changes in process conditions to be assessed for their implications on likely heat transfer performance.

Heat transfer enhancement by flow-induced vibration in heat exchangers

The flow-induced vibration in heat exchanger is usually considered as a detrimental factor for causing the heat exchanger damage and is strictly prevented from its occurrence. Its positive role for the possible heat transfer enhancement has been neglected. In this article a novel approach is proposed to enhance the heat transfer by using the flow-induced vibration of a new designed heat transfer device. Thus the flow-induced vibration is effectively utilized instead of strictly avoiding it in the heat exchanger design. A heat exchanger is constructed with the new designed heat transfer devices. The vibration and the heat transfer of these devices are studied numerically and experimentally, and the correlation of the shell-side convective heat transfer coefficient is obtained. It is found that the new designed heat exchanger can significantly increase the convective heat transfer coefficient and decrease the fouling resistance. Therefore, a lasting heat transfer enhancement by the flow-induced vibration can be achieved.

Heat transfer coefficients of shell and coiled tube heat exchangers

In the present study, the heat transfer coefficients of shell and helically coiled tube heat exchangers were investigated experimentally. Three heat exchangers with different coil pitches were selected as test section for both parallel-flow and counter-flow configurations. All the required parameters like inlet and outlet temperatures of tube-side and shell-side fluids, flow rate of fluids, etc. were measured using appropriate instruments. Totally, 75 test runs were performed from which the tube-side and shell-side heat transfer coefficients were calculated. Empirical correlations were proposed for shell-side and tube-side. The calculated heat transfer coefficients of tube-side were also compared to the existing correlations for other boundary conditions and a reasonable agreement was observed.

Feasible Design Space for Shell-and-Tube Heat Exchangers Using the Bell−Delaware Method

This paper presents an improved methodology for generating feasible regions for shell-and-tube exchanger design, taking into account geometric and operational constraints. The approach is based on the Bell−Delaware method to describe the shell-side flow with no simplification; this approach, therefore, can incorporate the entire range of geometric parameters of practical interest. Compact analytical equations are derived from the rigorous Bell−Delaware method for the shell-side heat transfer coefficient and pressure drop. These equations aid significantly in the solution of the design problem. The solution involves a nested approach where the compact equation parameters are treated as iteration variables; a simplified heat exchanger model is solved in an inner loop, and the exchanger parameters are updated in an outer loop. Compared to a previous work, which uses the approximate Kern method to describe the shell-side flow, the present one provides a better accuracy for the thermal design of shell-and-tube heat exchangers with single-phase fluids. One example is presented to show the application of the proposed method. The alternative use of proprietary design software is also illustrated.

Experimental determination of shell side heat transfer coefficient and pressure drop for an oil cooler shell-and-tube heat exchanger with three different tube bundles

In this paper, the heat transfer coefficient and pressure drop on the shell side of a shell-and-tube heat exchanger have been experimentally obtained for three different types of copper tubes (smooth, corrugated and with micro-fins). Also, experimental data has been compared with theoretical data available. Correlations have been suggested for both pressure drop and Nusselt number for the three tube types. A shell-and-tube heat exchanger of an oil cooler used in a power transformer has been modeled and built for this experimental work in order to investigate the effect of surface configuration on the shell side heat transfer as well as the pressure drop of the three types of tube bundles. The bundles with the same geometry, configuration, number of baffles and length, but with different external tube surfaces inside the same shell were used for the experiment. Corrugated and micro-fin tubes have shown degradation of performance at a Reynolds number below a certain value ( Re < 400). At a higher Reynolds number the performance of the heat exchanger greatly improved for micro-finned tubes.

3D simulation on the unit duct in the shell side of the ROD baffle heat exchanger

The ROD baffle heat exchanger can slightly enhance the shell side heat transfer coefficient with the significant reduction of pressure loss due to the shell side fluid flowing longitudinally through tube bundle, which leads to the reduction of the manufacture and running cost and in some cases to the dimensions reduction of the heat exchangers. Because of the complexities of fluid dynamics equations and the structure of heat exchangers, few theoretical researches have been accomplished to specify the shell side characteristics of the ROD baffle heat exchanger. A unit duct model in the shell side of the longitudinal flow type heat exchanger has been developed based on suitable simplification. A numerical analysis on shell side of the ROD baffle heat exchanger has been carried out at constant wall temperature to obtain the characteristics of heat transfer and pressure drop. The numerical results show that the ROD baffles placed vertically and horizontally in the unit duct continue to shear and comminute the streamline flow when the fluid crosses over the ROD-baffles, and change the fluid flow directions, and then the continuity and stability of the fluid are destroyed. The effect of disturbing flow can promote fluid turbulent intensity and effectively enhance heat transfer. The numerical analyses can provide the theoretical bases for optimizing the structure of ROD baffle heat exchanger and improving its performance.

Comparison of Heat Transfer and Pressure Drop for the Helically Baffled Heat Exchanger Combined with Three-Dimensional and Two-Dimensional Finned Tubes

Experiments were performed to compare the shell-side heat transfer coefficient and pressure drop of a helically baffled heat exchanger with petal-shaped finned tubes to those of low-finned tubes for oil cooling using water as a coolant. The experimental results showed that for the heat exchanger with petal-shaped finned tubes, the shell-side heat transfer coefficients were augmented by 28–48%, yet the shell-side pressure drops were reduced by 35–75% at the same volumetric flow rates of oil. The possible mechanisms responsible for this heat transfer enhancement were analyzed for helically baffled heat exchanger combined with petal-shaped finned tubes.

Effect of Inundation Upon the Condensation Heat Transfer Performance of R-134a: Part II—Results (RP-984)

Shell-side heat transfer coefficients were experimentally determined for three different types of tubes in a 25-tube bundle designed to simulate a single-pass heat exchanger. Smooth tubes, two-dimensional integral fin tubes, and three-dimensional enhanced-surface tubes were arranged in a three-column-by-ten-row staggered pattern with a horizontal and vertical pitch of 22.9 mm. Bundle average heat transfer coefficients and row-by-row heat transfer coefficients were measured as part of this study. Results showed the three-dimensional enhanced tube had the highest condensation heat transfer coefficient of any tube tested during the course of the study. Bundle average heat transfer coefficients for the three-dimensional tube showed a steady decline with increased heat flux and the row-by-row heat transfer coefficients showed an almost linear decrease with increased row number. The performance of the two-dimensional tube showed variations with heat flux but showed less sensitivity to inundation level. The experimental results for all tubes were compared with published correlations. Experimental results for the two-dimensional tube were predicted well by the correlations, but no suitable correlation was found for the three-dimensional tube so one was developed.

A new chart method for evaluating single-phase shell side heat transfer coefficient in a single segmental shell and tube heat exchanger

This paper presents a simple but accurate method to calculate shell side heat transfer coefficient in a single segmental shell and tube heat exchanger. The method is based on a chart which is a product of actual data taken over a span of several years. The calculation procedure is presented with a case study. The results are compared with known methods and commercial/proprietary computer codes prevalent in the industry. The results from this method compare well with HTRI computer program. This method can prove to be a helpful tool for design engineers in the field.

Experimental study on heat transfer enhancement of a helically baffled heat exchanger combined with three-dimensional finned tubes

Heat transfer and pressure drop of helically baffled heat exchanger combined with petal-shaped finned tubes for oil (ISO VG-32) cooling with water as coolant was experimentally studied. The tube side heat transfer coefficient was obtained by a modified Wilson plot technique. Results were presented as plots of the shell side heat transfer coefficient based on the actual outside surface area of tube bundle and pressure drop against volumetric flow rate of oil. Under experimental conditions, the maximum shell side heat transfer coefficient is 2265 W/m 2 K, the corresponding shell side pressure drop is 91 kPa. The preliminary heat transfer enhancement mechanisms were discussed for oil flow helically on outside surface of petal-shaped finned tubes.

04/00001 Application of spectrometric nuclear borehole logging for reserves estimation and mine planning at Callide coalfields open-cut mine: Charbucinski, J. and Nichols, W. Applied Energy, 2003, 74, (3–4), 313–322

This research focus on the fluid flow and heat transfer of water inside the segmental baffle shell and tube heat exchanger (SB-STHE) optimization using combined baffle and longitudinal ribbed tube configuration. Triangular and circular ribbed tubes are employed with disk baffle shell and tube heat exchanger (DB-STHE) and combined segmental-disk baffle shell and tube heat exchanger (CSDB-STHE). The fluid domain is simulated by SOLIDWORKS Flow Simulation (Ver. 2015). Obtained results are compared with experimental data and numerical results available in literature. Based on the obtained results under maximum mass flow rates (2 kg/s), the average value of shell-side heat transfer coefficient of DB-TR and CSDB-TR are 26.6% and 31.9% higher than DB-CR and CSDB-CR, respectively. To evaluate the performance, Q/ΔP is selected at the same flow rate. A 42.8%, 40.5%, 24.2% and 7.12% difference over conventional baffles are represented by DB-TR, CSDB-TR, CSDB-CR and DB-CR respectively. In another criterion named as Performance evaluation criterion a 39%, 37%, and 13% performance difference over conventional baffles are represented by disk baffle shell and tube heat exchanger with longitudinal triangular ribbed tube (DB-TR), combined segmental-disk baffle shell and tube heat exchanger with longitudinal triangular ribbed tube (CSDB-TR), and combined segmental-disk baffle shell and tube heat exchanger with longitudinal circular ribbed tube (CSDB-CR) respectively.

An Investigation of Condensation Heat Transfer Performance of HFC-134a on Single Enhanced Tubes (RP-984)

Tests to measure shell-side heat transfer coefficients were performed on a single-tube test facility. HFC-134a was condensed on the horizontal test tube with cold water working as the coolant. Two 19.1 mm (0.75 in.) outer diameter (OD) enhanced tubes, one a two-dimensional (2D) finned tube and the other a three-dimensional (3D) enhanced tube, were used to construct the test section. For comparison purposes, a smooth tube of the same nominal diameter was also tested. The experiments were conducted over a heat flux range of 3155 to 63 100 W/m2 (1000 to 20,000 Btu/h·ft2) at saturation temperatures of 40 and 45°C (104 and 113°F). The tests revealed that the shell-side heat transfer coefficient dropped as heat flux increased. The enhanced tubes significantly improved the condensation heat transfer effectiveness compared with the smooth tube, with the 3D enhanced tube having the highest heat transfer coefficients. Specifically, the 2D tube had heat transfer coefficients that were 8.0 times better than the smooth tube, whereas enhancements of 11.8 times were seen in the 3D tube. The heat transfer coefficients for each tube were also compared with existing single-tube models.