Primary Surface Heat Exchanger Research Articles

Analysis on heat transfer enhancement mechanism in a cross-wavy primary surface heat exchanger based on advection thermal resistance method

This paper numerically investigates the flow and heat transfer characteristics in the primary surface heat exchanger (PSHE) with cross-wavy (CW) structures. The comprehensive performance affected by hydraulic diameters is evaluated. Moreover, the airflow shuttling behavior at the mixing area of CW-type PSHE is discussed, showing rapid heat transfer enhancement. The advection thermal resistance method and local thermal resistance analysis is proposed, while the impacts of longitudinal pitch and flowrates are considered. Results show that the case with a large hydraulic diameter displays much better comprehensive performance at lower flowrates. When raising the hydraulic diameter from 1.58 mm to 15.8 mm, the heat transfer rate per unit pumping power grows by 36.1 %. However, the priority of large channel is gradually disappeared after increasing the flowrates. Meanwhile, the larger longitudinal pitch of the CW channel may result in pronounced improvement on the heat transfer performance due to the presence of airflow shutting behavior at the mixing area as well as the secondary flow near the channel boundary layers. When no airflow shuttling exists, very high advection thermal resistance region can be observed due to the formation of boundary layers. It can be recognized that the case with airflow shuttling behavior can display similar heat transfer improvement compared to that with increasingly high Reynolds numbers, yet the pressure loss is rarely increased.

Investigation of cross-wavy primary surface structures for heat exchangers of Brayton cycle system using argon

In order to investigate the performance of the Cross-Wavy (CW) primary surface heat exchanger in Brayton cycle system using argon, a three-dimensional numerical model is established in this paper, and the influence of the structural characteristics of the flow channel on heat transfer and flow is analyzed in depth based on numerical simulation results. Effects of amplitude (A), height (H) and thermal channel radius (R1) on pressure loss, heat transfer and overall performance are further investigated. The results indicate that the increase in A leads to a significant rise in heat transfer performance and energy loss. Compared with the maximum and minimum amplitude simulation results, the increase in the f coefficient can reach 140%, and the increase in Nu is 31.94%. With the increase of H from 1.7 mm to 3.2 mm, f decreases by 18.75% and Nu decreases by 8.07%. Whereas, the change brought about by R1 is very small, less than 2.5%. By comparing the f coefficients with the experimental results of the biconvex stamped plate heat exchanger, the feasibility of the CW primary surface heat exchanger for application in a micro nuclear power system is verified.

Study on the influence of circumferential shape on the performance of cross wavy primary surface heat exchanger channel

The primary surface heat exchanger can be described as a compact and highly efficient heat exchanger. In contrast, the cross wavy primary surface heat exchangers are suitable for microturbines. Based on the study of circular cross wavy channel, this study innovatively proposed the triangular cross wavy channel to improve the fluid flow conditions and the rectangular cross wavy channel to increase the overall heat exchange of the channel. The applicability domain of the three types of channels is summarized by numerical simulation. The circular cross wavy channels have the smallest irreversible loss, the triangular cross wavy channels have the highest efficiency and the rectangular channels have the largest total heat transfer. Moreover, the correlations of Nusselt number and friction factor are proposed. The correlations for the Nusselt number and friction coefficient have been validated, and the average absolute errors are 2.71 % and 7.85 % respectively. The results show that the correlation formulas can effectively predict the resistance and heat transfer performance of the cross wavy heat exchange channel.

Theoretical and numerical study on new evaluation criteria for longitudinal vortex enhanced heat transfer

The enhancement of heat transfer caused by longitudinal vortex phenomena has been a widely studied topic for a significant period in fluid mechanics and heat transfer. However, despite extensive efforts, the current understanding of longitudinal vortex flow and the involved physical mechanisms leading to enhanced heat transfer remains qualitative in nature. To unveil the physical mechanisms underlying the enhancement of convective heat transfer by longitudinal vortices, further quantitative research and in-depth discussions are necessary. By performing detailed derivations and proofs of the equations, this study aims to further understand the relationship between local vortex variations and heat transfer performance. The results indicate that the presence of longitudinal vortices alters the gradient of the convective term and ultimately leads to enhanced heat transfer performance. Based on the derived results, corresponding metrics have been proposed to quantitatively analyze the degree of heat transfer enhancement due to longitudinal vortices. This proposed quantitative analysis metric has been applied to evaluate the heat transfer performance of a cross-wavy primary surface heat exchanger, validating the reliability of the metrics. The research content and conclusions provide valuable insights for both theoretical investigations and practical engineering applications in the field of enhanced heat transfer.

Numerical Investigation of Heat Transfer and Erosion Characteristics of a New Waffle Primary Surface Heat Exchanger

Numerical Investigation of Heat Transfer and Erosion Characteristics of a New Waffle Primary Surface Heat Exchanger

Experimental study on heat transfer performance of fin-tube exchanger and PSHE for waste heat recovery

In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.

Experimental and numerical study on heat transfer and pressure drop performance of Cross-Wavy primary surface channel

The Cross-Wavy primary surface heat exchanger is one of the most promising candidates for microturbine recuperators. In this paper, naphthalene sublimation experiments are performed for Cross-Wavy channels in a wind tunnel. The experimental results indicate that the entrance region has a small effect on the unit-averaged heat transfer coefficient of whole Cross-Wavy channels. Correlations of Nusselt number and friction factor in the Cross-Wavy channel are obtained. However, only the Cross-Wavy channel with a large equivalent diameter is tested because the actual Cross-Wavy channels are very complicated and small. Therefore, based on the similarity rules, five Cross-Wavy channels with similar structures but different equivalent diameters are further investigated by numerical simulations. The numerical results indicate that the Cross-Wavy channels with similar structures but different equivalent diameters have similar thermal-hydraulic performance in the studied Reynolds number range.

Thermal Characteristics of a Primary Surface Heat Exchanger with Corrugated Channels

This paper presents the heat transfer and pressure drop characteristics of a primary surface heat exchanger (PSHE) with corrugated surfaces. The PSHE was experimentally investigated for a Reynolds number range of 156–921 under various flow conditions on the hot and cold sides. The inlet temperature of the hot side was maintained at 40 °C, while that of the cold side was maintained at 20 °C. A counterflow was used as it has a higher temperature proximity in comparison with a parallel flow. The heat transfer rate and pressure drop were measured for various Reynolds numbers on both the hot and cold sides of the PSHE, with the heat transfer coefficients for both sides computed using a modified Wilson plot method. Based on the results of the experiment, both Nusselt number and friction factor correlations were suggested for a PSHE with corrugated surfaces.

Numerical study on small-scale longitudinal heat conduction in cross-wavy primary surface heat exchanger

The longitudinal heat conduction is usually neglected during the analysis of cross-wavy (CW) primary heat exchanger. In this paper, an anisotropic heat transfer numerical model is proposed to analyze the local thermal field of primary surface plate affected by the small-scale longitudinal heat conduction. Moreover, a detached numerical model is used for simplifying grid and improving computational stability. It shows that the temperature distribution is non-uniform in the anisotropic heat transfer model. The small-scale longitudinal heat conduction makes the temperature distribution of plate become more uniform and enhances the heat exchanger performance. The temperature difference has little effect on the contribution of longitudinal heat conduction, while the contribution of longitudinal heat conduction increases with the increase of the inlet temperature and Reynolds number.

Recent development and application of several high-efficiency surface heat exchangers for energy conversion and utilization

In the present study, the recent research of three kinds of surface heat exchangers, i.e., shell-and-tube heat exchangers with helical baffles, air-cooled heat exchangers used in large air-cooled systems, and primary surface heat exchangers are reviewed. They are used in the energy conversion and utilization for liquid to liquid, gas to gas and liquid to gas heat exchange, respectively. It can be concluded that the helical baffled shell-and-tube heat exchangers (STHXs) should be used to replace the conventional segmental baffled STHXs in industries, despite there are a lot of research work have to be done, especially on the novel combined helical baffles. The primary surface gas to gas heat exchangers are developing towards to the more complex 3D CC primary surfaces, such as the double-wave CC primary surface, offset-bubble primary surface and 3D anti-phase secondary corrugation. The whole performance for the air-cooled heat exchangers in the air cooling system and the multi-objectives optimization for air-cooled heat exchangers should be paid more attention, considering the heat transfer, pumper power, space usage and other economic influence factors.

유기랭킨사이클(ORC)을 위한 주전열면 열교환기의 채널주름비에 따른 유동 및 열전달특성

Abstract A series of numerical simulation has been carried out to study thermo-hydraulic characteristics of a primary surfacetype heat exchanger, which is designed for the evaporator and condenser of a geothermal ORC. Working fluid is geothermalwater at hot side and R-245fa, which is a refrigerant designed for ORC, at cold side. Amplitude ratio of the channel andReynolds number are considered as design parameters. Nusselt number is presented for the Reynolds number ranging from50 to 150 and compared to analytic solutions. The result shows that higher amplitude ratio channel gives better heat transferperformance within the range of investigation. Key words ORC(유기랭킨사이클), Primary surface heat exchanger(주전열면 열교환기), Amplitude ratio(채널주름비), Friction factor(마찰계수), Nu(누셀트수)†Corresponding author, E-mail: jahn@kookmin.ac.kr 기호설명 A ： 채널진폭 [m] C p ： 비열 [J/kg-K] D h ： 수력직경 [m] f ： 마찰계수 H ： 채널높이 [m] h ： 대류열전달계수 [W/m 2 -K] k ： 열전도율 [W/m-k] L ： 채널길이 [m] ： 질량유량 [kg/s] Nu ： Nusselt 수∆ ： 압력강하 [Pa] q

Numerical study on the cross-corrugated primary surface heat exchanger having asymmetric cross-sectional profiles for advanced intercooled-cycle aero engines

Due to its high volume goodness and light weight, the cross-corrugated primary surface heat exchanger is a promising candidate for application to an advanced intercooled-cycle gas turbine engine. The asymmetric corrugation profile considered in this paper has the possibility of achieving balanced pressure drops on both hot and cold sides of an intercooler matrix, which may enable significant weight reductions not only in counter-flow designs, but also in cross-flow designs. For the assessment of its performance, a numerical procedure incorporating a detailed three-dimensional computational fluid dynamics model and a lumped parameter flow-network model has been investigated. By developing a new parameterization method for the shape of the profile, the detailed aero-thermal performance of the asymmetric profile is summarized quantitatively. A cross-flow heat exchanger matrix sizing study for matrix weight minimization is carried out, and the results show the high dependency of the potential improvements on the given operating conditions and design requirements.

An investigation of cross-corrugated heat exchanger primary surfaces for advanced intercooled-cycle aero engines (Part-I: Novel geometry of primary surface)

The present study aims to develop a novel cross-corrugated primary surface for an intercooler in an aero-engine. Cross-corrugated primary surface heat exchangers are proposed for such applications due to their relatively high “volume goodness” and thus the potential for light weight designs. In the present study, modified primary surface geometries were analyzed using three-dimensional numerical simulation. The fully developed airflow in a cross-corrugated matrix unit cell was modeled with a low-Reynolds number k–ε turbulence model using steady incompressible Reynolds-Averaged Navier–Stokes (RANS) equations. The numerical approach was validated against experimental data for conventional cross-corrugated surfaces. The calculated pressure drop and heat transfer capacity of the novel surfaces were assessed in terms of the Fanning friction factor and Nusselt number while the overall performance was estimated using the volume and area goodness factors. Finally, the investigation on the pressure loss mechanism was achieved through a simplified analysis of the entropy generation.

Experimental Study and Genetic-Algorithm-Based Correlation on Pressure Drop and Heat Transfer Performances of a Cross-Corrugated Primary Surface Heat Exchanger

Heat transfer and pressure drop characteristics of a cross-corrugated (CC) primary surface heat exchanger with different CC passages (P/H=2, θ=60 and 120 deg, called CC2-60 and CC2-120, respectively) in two air sides have been experimentally investigated in this study. It is shown that the corrugation angle (θ) and the ratio of the wavelength P to height H(P/H) are the two key parameters of CC passages to influence the heat transfer and flow friction performances. The heat transfer and friction factor correlations for these two configurations are also obtained with Reynolds numbers ranging from Re=450–5500(CC2-60) and Re=570–6700(CC2-120). At a certain P/H, the Nusselt number, Nu, and the friction factor, f, are affected by the corrugation angle, θ. The heat transfer performance of CC2-120 are much better than that of CC2-60 while the pressure drop of the former is higher than that of the latter, especially at high Reynolds numbers region. The critical Reynolds numbers at which the flow mode transits from laminar to turbulent in the two different passages are also estimated. Furthermore, in this study a genetic algorithm (GA) has been used to determine the coefficients of heat transfer correlations by separation of total heat transfer coefficient without any information of measured wall temperatures. It is concluded that the GA-based separated heat transfer Nusselt number provides a good agreement with the experimental data; the averaged relative deviation by GA (1.95%) is lower than that by regression analysis (2.84%). The inversely yielding wall temperatures agree well with the measured data in turn supporting the reliability of experimental system and measurements. It is recommended that GA techniques can be used to handle more complicated problems and to obtain both-side heat transfer correlations simultaneously, where the conventional Wilson-plot method cannot be applied.

Experimental study on flow and local heat/mass transfer characteristics inside corrugated duct

The present study investigates the flow and heat/mass transfer characteristics of wavy duct for the primary surface heat exchanger application. Local heat/mass transfer coefficients on the corrugated duct side walls are measured using a naphthalene sublimation technique. The flow visualization technique and a numerical analysis using a commercial code, FLUENT, are used to understand the overall flow structures inside the duct. The corrugation angle of the wavy duct is 145° and the duct aspect ratio is 7.3. The Reynolds numbers, based on the duct hydraulic diameter, vary from 100 to 5000. The results show that complex secondary flows and transfer processes exist inside the wavy duct resulting in non-uniform distributions of the heat/mass transfer coefficients on the duct side walls. At low Reynolds numbers ( Re ⩽ 1000), relatively high heat/mass transfer regions like cell shapes appear on both pressure- and suction-side walls due to the secondary vortex flows called Taylor–Görtler vortices perpendicular to the main flow direction. However, at high Reynolds numbers ( Re > 1000), these secondary flow cells disappear and boundary layer type flow develop on pressure-side wall. On the suction-side wall, high heat/mass transfer region appears by the flow reattachment. The average heat/mass transfer coefficients are higher than those of the smooth circular duct and pressure drop increases due to the secondary flows inside wavy duct.

5555933 Primary surface heat exchanger for use with a high pressure ratio gas turbine engine

5555933 Primary surface heat exchanger for use with a high pressure ratio gas turbine engine

Experimental Investigation of Gas Turbine Recuperator Fouling

This paper discusses an experimental investigation of recuperator fouling currently underway at the David Taylor Naval Ship Research and Development Center. The overall approach involves testing different heat exchangers in the exhaust gas stream of a gas turbine. The two heat exchangers initially tested were the plate-fin type and differed in the gas-side heat transfer surface geometry. Primary surface heat exchangers are being considered for future tests also. Test conditions are defined such that the critical part of full-scale recuperators (i.e., the colder end of the gas passages) is simulated in the small test heat exchangers. The composition of the gas stream is measured to determine amounts of gaseous, particulate, and condensible hydrocarbon emissions. Fuel samples taken during each test are analyzed. The test heat exchangers are specially constructed to allow inspection and measurement of the fouling film inside the unit following each test. The temperature distribution inside the test exchanger is measured, as well as air and gas inlet and exit temperatures. Measurements of fouling film thickness are made using an optical microscope and photographs of fouling deposits were taken. The early results obtained from fouling tests conducted with the first heat exchanger are discussed. Tests were also conducted to demonstrate a fouling removal technique.