Manifold Arrangement Research Articles

Optimizing horizontal manifold arrangement for ground source heat pump using orthogonal testing

This study investigates the importance of improving the heat transfer efficiency of buried pipe systems by optimising the horizontal manifold layout in ground source heat pump systems under summer conditions. Based on the similarity theory, we developed a novel horizontal manifold layout method on a sandbox experimental bench. The heat loss of horizontal manifold in different scenarios (underground garage, lawn, square and road) was investigated by orthogonal tests. The study identifies the optimal layout of the horizontal manifold for different scenarios, with a special focus on how the new layout can effectively reduce the outlet temperature in a 20 ℃ underground garage environment. The new solution improves the overall heat transfer performance of the system by 37 % compared to the traditional horizontal manifold layout. The study highlights that even if individual component efficiencies are not optimal, a sensible system configuration can still optimise overall performance, and synergies between components need to be considered. Extreme variance analysis reveals the influence of five key factors on the heat transfer efficiency of the horizontal manifold, with surface temperature having the most significant effect. This study provides an integrated optimisation approach for ground source heat pump systems, which is particularly suitable for diverse application scenarios. These findings not only improve the performance of ground source heat pump systems, but also provide valuable guidance for practical engineering design, offering new perspectives on the application and optimisation of ground source heat pump systems.

Investigation of Z-type manifold microchannel cooling for ultra-high heat flux dissipation in power electronic devices

Ultra-high heat flux (up to 1000 W/cm2) thermal management has been an urgent need for advanced power electronic devices to maintain their superior electrical performance and reliability. Embedded microchannel cooling is a promising and challenging thermal management method for high-heat-flux chips. This study presents an embedded Z-type manifold microchannel (Z-MMC) cooling design for a 5 × 5 mm2 heating zone, which can dissipate an ultra-high heat flux up to 1842 W/cm2 by using water single-phase flow. The microchannel array is etched on silicon wafer, while the manifold structure is fabricated by PDMS molding. The test chips are assembled using O2 plasma bonding technique, which provides an observation window for visualizing the flowing state of the coolant during the heat transfer process. We experimentally test and compare four test chips with different microchannel geometries and manifold designs. The average heater temperature, temperature distribution, thermal resistance, heat transfer coefficient and pressure drop are reported for mass flow rates of 2–6 g/s. The proposed Z-MMC cooler is capable of dissipating up to 1800 W/cm2 with a total thermal resistance of only 0.075 cm2·K/W (only 0.039 cm2·K/W after subtracting the conduction thermal resistance), at a flow rate of 6 g/s and a pressure drop of 54 kPa. Compared to the rectangular manifold arrangement, the trapezoidal manifold demonstrates a lower temperature rise, a more uniform temperature distribution and a smaller pressure drop at the same heat flux and flow rate, mainly due to a more uniform fluid distribution in the microchannel. Furthermore, we compare our proposed design's thermo-hydraulic performance with those of representative manifold microchannel cooling data in the literature, and the proposed Z-MMC design demonstrates relatively low thermal resistance and pressure drop values.

Numerical investigation of novel manifold microchannel heat sinks with countercurrent regions

Manifold microchannel (MMC) heat sink is a potential method to dissipate high heat fluxes of electronic devices. Traditional Z-type MMC is a simple configuration but usually encounters high temperature difference and pressure drop. In this work, we introduced countercurrent flows to alleviate these problems by revising the design of manifold configurations. Six cases with different manifold arrangements are numerically investigated using single-phase deionized water at mass flow rates ranging from 0.04 - 0.12 g/s. The results show that the maximum temperature, average temperature, and temperature difference of the revised arrangements are all lower than these of the traditional Z-type manifold arrangement. The cases with countercurrent regions can reduce the maximum temperature around 5 K compared with the original cases with parallel regions. The temperature difference of the ZU-type MMC with double-layer countercurrent flow configuration is lower than 4 K, which is about 25% of the original Z-type MMC. For the revised manifold configuration with countercurrent flows, the pressure drops also decrease due to the split of inlets and outlets of the manifold. The pressure drops of single-layer and double-layer countercurrent manifolds are respectively 27.13% and 33.36% lower than that of the case with traditional Z-type manifold. This leads to a higher comprehensive performance of revised cases with countercurrent flows. Besides the better temperature uniformity, the fluid flow becomes more uniform in the microchannels for the revised case. The improved ZU-type MMC with double-layer countercurrent flow can dissipate 1100 W/cm2 for single-phase flow with a temperature increase of 80 K and a pressure drop of 22 kPa at mass flow rate of 1.2 g/s.

Thermal and hydrodynamic characteristics of single-phase flow in manifold microchannels with countercurrent regions

Manifold microchannel heat sink is promising to dissipate high heat fluxes for electronic devices due to its high surface to volume ratio. Traditional Z-type manifold encounters fluid flow maldistribution and a high temperature difference. In this work, two inlets and countercurrent flows are introduced into the manifold arrangement to alleviate these problems in the Z-type manifold microchannels. Six cases with different manifold arrangements are numerically investigated using single-phase HFE-7100 at mass flow rates ranging from 56.8 to 117.78 mg/s. The results show that the maximum temperature, average temperature, and temperature difference of the revised arrangements are all lower than these of the traditional Z-type manifold arrangement. The minimum temperature difference for an ideal multi inlet manifold arrangement can be less than 0.2 K, while the value is about 5.3 K for the traditional Z-type manifold arrangement. The revised arrangement can also improve the uniformity of mass flux distributions. The ratio of the maximum to the minimum mass flux within microchannels is 12.83 for the traditional Z-type manifold, while this value is about 5.82 for cases with two inlets and countercurrent zones. A longer flow path and a higher local pressure drop in the revised arrangements results in higher pressure drops than the traditional Z-type manifold microchannels. Compared with the traditional Z-type arrangement, heat transfer coefficients and performance evaluation criterion are higher for the improved cases. The presence of a countercurrent zone can improve the comprehensive performance of the manifold microchannel. New criterion based on the thermal resistance calculated at the maximum temperature is proposed to evaluate the cooling performance of electronics.

Observational Analysis of Stationary C.I. Engine Output and Emission Evaluation for Variance of Induction Pressure Aspects

In the current environment, improved engine performance, reduced fuel consumption and reduced emissions are important goals for automotive manufacturers. To understand the factors involved in the compartment assemblies in Compression Ignition (C I) engines it is crucial to concentrate on such goals. Pressure rating, fuel atomization, fuel pressure, fuel quality, air pressure rating, air temperature, pressure and other design components such as piston, Air induction system, and assembly chamber and more to work. It is evident from the literature review and research work carried out to date that the airing system is best method of promoting C I operation of the engine. The design of the Air suction system could be achieved in this way that it takes into account the objectives of entire system. Effective air suction system improvement needs least energy utilization and most extreme use of air intake pressure for decrease in poisonous productions at outlet of C I engines. Furthermore, powerful use of fuel vitality. In present work, air suction arrangement, exclusively less air inlet pressure during suction stroke of four stroke cycle engine concern is topic of explicit enthusiasm for plan. Advancement of air induction system with air induction pressure regulator, flow distribution, action is studied and useful information is developed through proper intake manifold arrangement for better fuel efficiency.

Investigation of flow and heat transfer performance of the manifold microchannel with different manifold arrangements

The manifold microchannels (MMC) plays an essential role as an efficient method for heat dissipation in electronic devices. In this study, the flow and heat transfer characteristics of MMC with different manifold structures are investigated by numerical simulation. The results show the excellent effect of manifold optimization in alleviating the uneven fluid distribution between the microchannels and reducing the pressure loss of the MMC. It is observed that manifold optimization reduces the thermal resistance and temperature difference of the MMC. Finally, the comprehensive performance of different manifold structures is evaluated by the PEC value and their relationship among the pressure drop ratio, temperature difference ratio and thermal resistance ratio. And it is found that the parabolic-type manifold provides the best comprehensive performance. By analyzing the effect of conical manifold, parabolic manifold and elliptical manifold on the flow distribution, it was concluded that the uniform distribution of fluid in the MMC can be achieved by controlling the converging rate of the manifold. • The pressure drop of the manifold microchannel with tapered-type manifold is the smallest. • The optimized structures of manifold can improve uneven flow distribution among microchannels. • Parabolic-type manifold demonstrates the best comprehensive performance. • Uniform distribution of fluid can be achieved by controlling the arrangement of the manifold.

Investigation of Flow and Heat Transfer Performance of the Manifold Microchannel with Different Manifold Arrangements

Investigation of Flow and Heat Transfer Performance of the Manifold Microchannel with Different Manifold Arrangements

Retraction Note to: An experimental study on microchannel heat sink via different manifold arrangements

Retraction Note to: An experimental study on microchannel heat sink via different manifold arrangements

Single-phase and Two-phase Flow and Heat Transfer in Microchannel Heat Sink with Various Manifold Arrangements

The manifold microchannel (MMC) heat sink, which possesses better heat transfer performance and less pressure drop than the traditional microchannel heat sink, has attracted much attention from researchers in recent years. But not much of them, either single-phase or two-phase ones, focused on the problems about flow maldistribution and wall temperature nonuniformity that might ultimately lead to system breakdown. To investigate the flow distribution in the MMC heat sink, six types of manifold, namely Z-type, C-type, H-type, U-type, ZU-type, and HU-type are considered in the current study. All six manifolds are investigated in single-phase cases with water, while the latter three are adopted in two-phase cases with HFE7100. The cases are solved with the self-developed codes based on the OpenFOAM package. The manifold arrangement has a strong impact on the overall heat transfer performance and pumping power required. The HU-type and ZU-type MMC heat sinks are recommended to be fabricated in the single-phase heat transfer application due to their small thermal resistance lower than 2×10−5 m2·K/W and pressure drop less than 500 Pa. Besides, if the pumping power is not a restriction factor in the system, Z-type MMC is also recommended. In the two-phase cases, the flow distribution is naturally not uniform within a parallel microchannel system, and the microchannels with large flow velocity appear to have higher wall temperatures. The authors recommend using HU-type MMC heat sink in the flow boiling application due to its bottom wall temperature distribution is relatively uniform with a difference of less than 2 K.

A Method for Pump Manifold Performance Calculations in Hydraulic Air Compressors

Abstract Analytical methods are described that were developed to undertake the pump manifold calculations for hydraulic air compressors (HACs) where multiple pumps are installed in parallel configurations. The procedures are fast and exact and were developed for design optimization and control tasks which, although described in the specific context of HACs, are also applicable to more general pumping systems. The proposed method uses a recursive/iterative procedure to establish the pump curve equivalent to the pump combination so that the design performance of the system can be assessed for any value of externally attached hydraulic resistance. The technique is verified against a numerical method applied to the same problem, but where the external hydraulic resistance must be completely specified for a solution. Losses at convergent and divergent wyes, which are required to create the parallel pump manifold arrangements, are found to be significant factors in establishing the overall energy efficiency of the pumping system. With efficient pump manifold arrangements designed, a so-called binary pumping scheme is explained, where individual pumps in the manifold can be activated (1) or deactivated (0) so that the pumping system flow can be reduced with good turn-down ratios while ensuring that the best efficiency point (BEP) efficiency of the system is maintained (exemplified with 4:1 or 25%).

On topological classification of Morse–Smale diffeomorphisms on the sphere S n (n > 3)

We consider the class G(S n ) of orientation preserving Morse–Smale diffeomorphisms of the sphere S n of dimension n > 3, assuming that invariant manifolds of different saddle periodic points have no intersection. For any diffeomorphism f ∈ G(S n ), we define a coloured graph Γ f that describes a mutual arrangement of invariant manifolds of saddle periodic points of the diffeomorphism f. We enrich the graph Γ f by an automorphism P f induced by dynamics of f and define the isomorphism notion between two coloured graphs. The aim of the paper is to show that two diffeomorphisms f, f′ ∈ G(S n ) are topologically conjugated if and only if the graphs Γ f , Γ f ′ are isomorphic. Moreover, we establish the existence of a linear-time algorithm to distinguish coloured graphs of diffeomorphisms from the class G(S n ).

A comparative numerical study on two-phase boiling fluid flow and heat transfer in the microchannel heat sink with different manifold arrangements

The manifold microchannel (MMC) heat sink system has been widely used in high-heat-flux chip thermal management due to its high surface-to-volume ratio. Two-phase, three-dimensional numerical methods for subcooled flow boiling have been developed using a self-defined solver based on OpenFOAM. Four different types of manifold arrangements (Z-type, C-type, H-type and U-type) have been investigated at a fixed operational condition. The numerical results evaluate the effects of flow maldistribution caused by different manifold configurations. Before simulating the two-phase boiling flow in MMC metamodels, single-phase liquid flow fields are performed at first to compare the flow maldistribution in microchannels. It can be concluded from the flow patterns that H-type and U-type manifolds provide a more even and a lower microchannel void fraction, which is conducive to improving the temperature uniformity and decreasing the effective thermal resistance. The simulation results also show that the wall temperature difference of H-type (0.471 K) is only about 10% of the Z-type (4.683 K). In addition, the U-type manifold configuration show the lowest average pressure drop at the inlet and outlet of the MMC metamodel domain. However, H-type manifold also shows an impressive 59.9% decrease in pressure loss. Results indicate that both the H-type and the U-type manifolds for flow boiling in microchannels are recommended due to their better heat transfer performance and lower pressure drop when compared with Z-type and C-type.

An experimental study on microchannel heat sink via different manifold arrangements

The current experimental study performed the overall performance of the microchannel heat sink using the heat transfer coefficient, Nusselt number, and pressure drop for three novel manifold configurations. These selected manifolds have a rectangular (R), rectangle with semicircular (RSC) and divergent–convergent (DC) shapes for inlet and outlet. The heat transfer coefficient for all three types of microchannel was reported for the Reynolds number range of 342–857. The experiments were tested at four different heat inputs ranges between 50–125 W. R-type microchannel heat sink showed the worst performance, while the performance of DC-type microchannel heat sinks was the best. At Re of 342, the lowest Nusselt number was observed to be 2.8 at lower Reynolds number 342 for R-type manifold. RSC manifolds MCHS seems to be a better choice compared to R-type and DC-type MCHS with respect to pressure drop and Nusselt number. Compared to R-type microchannel heat sink, 24–32% and 7–10% augmentation in heat transfer coefficients were reported for DC-type and RSC-type microchannel heat sinks, respectively. Based on the released experimental results, it can be stated that DC-type microchannel heat sink is more beneficial in terms of heat transfer enhancement.

Fluid Flow in Microchannel Heat Sinks for various Flow Configurations in Tapered Manifold Arrangements

Micro channels face several types of thermal engineering challenges from different levels of heat generation. The reduction of the available surface area for sufficient heat removal becomes mandatory. If the working temperature of the component becomes very high in the absence of the sufficient heat removal, leads to a critical failure. So working fluid and flow configuration plays an important role. In the present work, CFD analysis of flow on U, P, S type micro channels heat sinks with tapered manifold arrangements is presented. At Reynolds number 705-1410 and with different heat inputs, the P type flow configuration is better than U-type and then followed by S-type flow configuration.

Numerical study on flow and heat transfer of a hybrid microchannel cooling scheme using manifold arrangement and secondary channels

The flow and heat transfer characteristics of a novel hybrid microchannel heat sink with manifold arrangement and secondary oblique channels (MMC-SOC) are numerically studied. Through the relationship between the total thermal resistance ratio (Rt/Rt0) and pressure drop ratio (ΔP/ΔP0), we define a region named Design Optimization Area (DOA), where the pressure drop ΔP and the total thermal resistance Rt can be both reduced due to the secondary channels. The numerical results show that the best heat sink can reduce ΔP by 1.91%, and simultaneously decrease Rt by 19.15% compared to the original MMC heat sink at Re = 295. In addition, the effects of secondary channel on ΔP are dependent on both the geometrical parameters and Reynolds numbers. On the one hand, it can reduce the pressure loss at small Reynolds numbers for most heat sinks. However, it can also increase the pressure loss at high Reynolds numbers for most heat sinks. As Re increases, the ratio (Rt/Rt0) becomes smaller and (ΔP/ΔP0) becomes larger, indicating a better thermal performance and a worse hydraulic performance. The secondary flow field analyses visually show the hydraulic and thermal performance enhancements due to thermal boundary layer re-development and flow mixing.

A computation analysis on flow distribution in microchannel under Triangular manifold arrangement system

Background/Objectives: In this paper, a complete study and CFD analysis is performed on triangular manifolds and heat sink assembly with the help of different input parameters. The objective of the study is to get exact understanding of the temperature variation, pressure drop, and velocity variations at inlet and outlet of manifold when we pass fluid from one manifold to another by giving different heat inputs to the heat sink. CFD analysis for the simulation purpose is performed on the geometry for the evaluation of heat transfer coefficient, Nusselt number and Reynolds number. Methods/Statistical Analysis: In this study, for simulation CFD analysis of the geometry with different input parameters (velocity, density, viscocity specific heat, thermal conductivity, heat flux) is a simple method applied for the for different temperature and pressure drop values at inlet and outlet. Three arrangements for the water flow (U, S, and P) are designed in the manifolds through the heat sink. Four heat input values (5.06W, 7.53W.10.12W, 12.65W) are selected for the simulation. Findings: CFD investigation was performed with microchannel setup having 20 rectangular channels of 0.0005m width, 0.0025m depth and 0.2m length with two triangular manifolds. Five input parameters (velocity, density, viscosity. specific heat, and thermal conductivity) and 24 numbers of experiments were performed with one temperature value at inlet (25°C) for the comparison of temperature and pressure drop values. After the analysis, observation was found that temperature had different values at outlet of manifold in each fluid flow arrangement (U, S and P type) the Reynolds number range is varying from 599 to 899.The results show that the fluid flow was better in U type fluid flow arrangement and the value of heat transfer coefficient (96.57w/m2c to 161.52w/m2c) is highest (2-3%) in comparison to S and P Type simulation. Applications: Triangular Manifolds are designed for providing uniform fluid flow and efficient heat transfer rate through the microchannel heat sink. As according to observation observed in the study, triangular manifolds have better heat transfer rate and it can be integrated in the next generation high temperature reactors. The manifolds are capable for use in fuel cells, liquid rocket engines, commercial heating and cooling and in automobiles. Keywords: Heat Transfer Rate, Microchannel Heat Sink, Nusselt Number, Reynolds Number, Triangular Manifolds

Unsteady Responses of the Impeller of a Centrifugal Compressor Exposed to Pulsating Backpressure

The flow in intake manifold of a heavily downsized internal combustion engine has increased levels of unsteadiness due to the reduction of cylinder number and manifold arrangement. The turbocharger compressor is thus exposed to significant pulsating backpressure. This paper studies the response of a centrifugal compressor to this unsteadiness using an experimentally validated numerical method. A computational fluid dynamic (CFD) model with the volute and impeller is established and validated by experimental measurements. Following this, an unsteady three-dimensional (3D) simulation is conducted on a single passage imposed by the pulsating backpressure conditions, which are obtained by one-dimensional (1D) unsteady simulation. The performance of the rotor passage deviates from the steady performance and a hysteresis loop, which encapsulates the steady condition, is formed. Moreover, the unsteadiness of the impeller performance is enhanced as the mass flow rate reduces. The pulsating performance and flow structures near stall are more favorable than those seen at constant backpressure. The flow behavior at points with the same instantaneous mass flow rate is substantially different at different time locations on the pulse. The flow in the impeller is determined by not only the instantaneous boundary condition but also by the evolution history of flow field. This study provides insights in the influence of pulsating backpressure on compressor performance in actual engine situations, from which better turbo-engine matching might be benefited.

Study of the Possibility of Achieving the Same Per-Port Outflow in a Dividing Manifold

There have been several attempts to optimise fluid flow manifolds; these, however, have shown are limited and further investigation into the efficiency of these systems is needed. This work focuses on improving the distribution manifolds efficacy in outflow division, i.e. attaining the same flow rate per each exit port of the manifold. Water has been selected to be the working fluid. A numerical investigation utilising CFD (by ANSYS Fluent R16.2) analysis into two-dimensional, incompressible, and turbulent flow has been carried out to resolve the flow manifold problem using two turbulence modelling, Standard k-ε and RNG k-ε, approaches. Four values of flow rate have been considered, which are specified by the Reynolds numbers 101×103, 202×103, 303×103, and 404×103. These values correspond to the fluid inlet velocities 0.5, 1.0, 1.5, and 2.0 m/s, respectively. The manifold configuration is defined by the given area ratio (total cross-sectional area for laterals /header cross-sectional area). Three values of area ratio are considered; these are 0.703125, 0.84375, and 0.984375. The results indicate that the flow uniformity has a reverse proportional relationship with the fluid flow rate and area ratio for all manifold arrangements. However, there is no significant effect of the flow rate increase on flow mal-distribution. Also, the use of RNG k-ε model has shown higher values of the non-uniformity coefficient than those obtained by the Standard k-ε model. The outcomes of this analysis have been compared with experimental data and a good agreement among them has been found.

CFD and Heat Transfer Analysis of Microchannel Heat Sink with Different Inlet and Outlet Flow Arrangements

The overall performance of microchannel heat sink (MCHS) as a system is affected by the inlet and outlet manifold arrangements in addition to array of microcannel. In the present study the CFD analysis is performed w.r.t the heat transfer coefficient, and Nusselt number for three different manifold arrangements. In the present work three different arrangements: Rectangular (R), Rectangle with Semi-Circular (RSC) and Divergent Convergent (DC) of the inlet and outlet manifolds are selected. The result shows MCHS within the Reynolds number ranging from 342-857, the DC type manifold has highest heat transfer coefficient (9%-10%) in comparison to RCS and R type manifold being the lowest.

Bifurcations and degenerate periodic points in a three dimensional chaotic fluid flow.

Analysis of the periodic points of a conservative periodic dynamical system uncovers the basic kinematic structure of the transport dynamics and identifies regions of local stability or chaos. While elliptic and hyperbolic points typically govern such behaviour in 3D systems, degenerate (parabolic) points also play an important role. These points represent a bifurcation in local stability and Lagrangian topology. In this study, we consider the ramifications of the two types of degenerate periodic points that occur in a model 3D fluid flow. (1) Period-tripling bifurcations occur when the local rotation angle associated with elliptic points is reversed, creating a reversal in the orientation of associated Lagrangian structures. Even though a single unstable point is created, the bifurcation in local stability has a large influence on local transport and the global arrangement of manifolds as the unstable degenerate point has three stable and three unstable directions, similar to hyperbolic points, and occurs at the intersection of three hyperbolic periodic lines. The presence of period-tripling bifurcation points indicates regions of both chaos and confinement, with the extent of each depending on the nature of the associated manifold intersections. (2) The second type of bifurcation occurs when periodic lines become tangent to local or global invariant surfaces. This bifurcation creates both saddle-centre bifurcations which can create both chaotic and stable regions, and period-doubling bifurcations which are a common route to chaos in 2D systems. We provide conditions for the occurrence of these tangent bifurcations in 3D conservative systems, as well as constraints on the possible types of tangent bifurcation that can occur based on topological considerations.