Pump Power Consumption Research Articles

Numerical investigation to optimize the modified cavity receiver for enhancement of thermal performance of solar parabolic dish collector system

The concentrated parabolic dish collector (PDC) systems are widely utilized for the purpose of generating high-temperature heat by receiving and converting solar energy efficiently into thermal energy. Cavity receivers including spiral coils have a common use in PDC system for optimal thermal performance. Therefore, to enhance the thermal performance of a PDC system, the present study investigates different cavity receiver configurations, such as cylinder and conical shaped receivers with flat and spherical absorber surface as well as the effect of spiral coil arrangement. To identify the most optimal spirally coiled cavity receiver, the comparison is conducted based on outlet temperature, heat exchange rate, thermal efficiency, effectiveness, and thermal performance capability (TPC). The investigations were conducted using the ANSYS Fluent CFD simulation software package. The SolTrace software package was utilized to compute the maximum heat flux incident on the absorber surface of the receiver, and peak heat flux data was used as input parameter at the absorber surface of the receiver. Furthermore, to select the suitable working fluid in PDC system, different heat transfer fluids, such as Syltherm 800, Xceltherm 600, ParathermHR™ and water, respectively were studied. From the thermal analysis of various proposed receiver geometries, the receiver with conical shape and spherical absorber surface is more efficient over other configurations. It provides 50 % higher heat transfer rate thancylindrical receiver with flat absorber surface. Moreover, receiver's thermal performance could modestly be improved by modifying the spiral coil pitch (variable pitch). In terms of pumping power consumption, readily availability, low viscosity, and high specific heat, water is suggested as working fluid for receiver of PDC system.

Multiphysics Simulation of a Novel Self-Adaptive Chip Cooling with a Temperature-Regulated Metal Pillar Array in Microfluidic Channels

Conventional liquid cooling techniques may provide effective chip cooling but at the expense of high pumping power consumption. Considering that there is dynamic heat load in practice, a self-adaptive cooling technique is desired to reduce operational costs while preserving inherent cooling effectiveness. In this work, a novel self-adaptive cooling strategy is presented to balance the thermal and flow efficiency in accordance with the dynamic thermal load, based on temperature-regulated movement of the metal pillar array in a microfluidic channel. With an illustrative device, the effectiveness of such a strategy is investigated using multiphysics modeling and simulation. As a case study, the device is considered to be initiated with a chip power of 5 W and an inlet coolant velocity of 0.3 m/s. It is shown that the temperature-regulated movement of the metal pillar heat sink will be activated rapidly and equilibrate within 30 s. Parts of the metal pillars immerse into the coolant flow, resulting in significantly improved heat transfer efficiency. The diminished thermal resistance leads to a reduction in chip temperature rise from 225 K (without structural adaptation) to 91.86 K (with structural adaption). Meanwhile, the immersion of metal pillars into the coolant also causes an increased flow resistance in the microfluidic channel (i.e., pressure drop increases from 859.27 Pa to 915.98 Pa). Nevertheless, the flow resistance decreases spontaneously when the working power of the chip decreases. Comprehensive simulation has demonstrated that the temperature-regulated structure works well under various conditions. Therefore, it is believed that the presented self-adaptive cooling strategy offers simple and cost-effective thermal management for modern electronics with dynamic heat fluxes.

Suitability of Embedded Liquid Cooling and Heat Generation for Chips.

Embedded liquid cooling is a preferred solution for dissipating the heat generated by high-power chips. The cooling capacity and pump power consumption of embedded liquid cooling heat sinks differ significantly between different structures. To achieve an accurate match between cooling capacity and heat dissipation requirements, the selection of a liquid-cooled heat sink should be carefully considered in conjunction with the heat dissipation needs of heat sources in real-world thermal management issues. Based on the manufacturing limitations on chip temperature and microchannel pressure, a composite performance index function was developed to assess the cooling capacity and cooling cost of the heat sink. This allowed for the establishment of an evaluation standard to determine the suitability of embedded liquid cooling and heat sink for the heat source. In this study, the suitability of four microchannel heat sinks with the same feature length and fin volume was evaluated under various thermal load conditions. The results show that the best-suited heat sink changes with variations in the thermal load of the chip. In the example, when the heat source was homogeneous at 100 W, the circular section pin fins have an optimal suitability of 0.928 for Re = 500. When the heat source was a heterogeneous heat source with a power of 100 W, the value of Θ was found to be 0.389. Additionally, the optimal suitability of drop section pin fins for Re = 971.5 was determined to be 0.862.

Constructal design of a rectangular porous fin considering minimization of maximum temperature difference and pumping power consumption

Constructal design of a rectangular porous fin considering minimization of maximum temperature difference and pumping power consumption

A comparative numerical investigation of the thermal-fluid phenomena between helium and nitrogen cooled pebble bed reactors

The study assesses the thermal-hydraulic performance of a pebble bed type nuclear reactor using nitrogen and helium as coolants. The analysis is done in two separate parts using CFD. First, a segment of the pebbles is modeled and later the whole reactor core. The study assesses the core performance under normal and after reactor shutdown conditions using these two different coolants. The assessment concludes that nitrogen as a coolant candidate for PBR behaves in an acceptable manner in both conditions at a cost of increased pumping power consumption. It is found that under steady state conditions, the heat stored in the pebbles (both for the segment and the whole core) is more in the case of the nitrogen cooled bed compared to the helium cooled bed.

A Novel Liquid Cooling Battery Thermal Management System With a Cooling Plate Based on Biomimetic Fractal Channels

Abstract An effective battery thermal management system (BTMS) is necessary to quickly release the heat generated by power batteries under a high discharge rate and ensure the safe operation of electric vehicles. Inspired by the biomimetic structure in nature, a novel liquid cooling BTMS with a cooling plate based on biomimetic fractal structure was proposed. By developing the physical model of the BTMS, numerical calculations were conducted to analyze the impacts of the structural parameters of the cooling plate and the inlet velocity of the coolant on the thermal performance of the batteries. The results showed that the cooling plate can meet the heat dissipation requirements of high-temperature uniformity for the batteries under high discharge rates, especially under the extremely uniform channel distribution mode for the adjacent fractal branch at the same level. Moreover, the increase in the group number of fractal branches can improve the cooling capacity of the cooling plate and reduce the pressure drop of the coolant. The increase in the level number of channels, the length ratio, and the inlet velocity of the coolant can enhance the cooling capacity. However, these methods of enhancing heat transfer require more pump power consumption. When the group number of fractal branches is 4, the level number of channels is 3, the length ratio is 1, and the inlet velocity of the coolant is 0.5 m/s, the BTMS can control the maximum temperature and maximum temperature difference of the batteries under 4C-rate discharge within 31.68 °C and 4.15 °C, respectively. Finally, orthogonal test was conducted on four factors: the group number of fractal branches, the level number of channels, the length ratio, and the inlet velocity of the coolant. The results showed that the level number of branches is the most important structural parameter.

Parametric analysis on thermal-hydraulic characteristics in variable-direction twisted-oval tube bundle in cross-flow

In this paper, numerical investigations on heat transfer and flow resistance characteristics of a variable-direction twisted-oval tube (VDTOT) were performed. The effects of different geometric parameters (transverse and longitudinal tube pitches, ratio of major to minor axis, twist angle and pitch) on the heat transfer coefficient, pressure drop and heat transfer capacity per pump work were investigated. Contribution ratios of different factors were also analyzed. The results show that the transverse tube pitch and twist angle have a great impact on the overall performance of the tube bundle. VDTOT realizes the synergistic enhancement of flow and heat transfer performance. Compared to the circular tubes, the heat transfer capacity of VDTOT bundles is increased by 13.6%–20.6 % under the same pump power consumption. The average deviations of Nu and Eu correlations fitted by the multiple regression method are 0.99 % and 1.64 %, which is helpful for the rapid design and optimization of VDTOTs.

Study on the cooling performance of a new secondary flow serpentine liquid cooling plate used for lithium battery thermal management

To improve the thermal and economic performance of liquid cooling plate for lithium battery module in the distributed energy storage systems, on the basis of the traditional serpentine liquid cooling plate, the unidirectional secondary channels and grooves are added, combined to three kinds of serpentine cold plates for the battery module. By contrast, the cold plate with both elliptical groove and secondary channel has the best comprehensive performance. Though the thermal performance is slightly reduced, the consumption of pump power is reduced by 92.6 % and the cooling efficiency coefficient is improved by 12.32 times compared to the original cold plate. The cooling temperature targets of the battery pack are that Tmax less than 40℃ and ΔTavg less than 3 K. In order to achieving the best performance of the cold plate, the influence of the structural parameters and hydrodynamic parameters on the performance index is analyzed, and the sensitivity analysis is carried out which clear the operational mechanism and key design parameters of the cold plate. The results show that different design parameters would generate the change of eddy current which is influential to the cooling performance. Besides, v and D have a significant effect on the performance of the cold plate, followed by d and n, and a has almost no effect on the cooling performance.

Thermal performances of pumped thermosyphon loops with evaporator configured by serpentine ribbed channel with and without internal effusion

Thermal performances of two pumped thermosyphon loops (PTL) with the evaporator configured by the serpentine ribbed channel with or without the internal effusion are studied. The boiling flow structure, thermodynamic cycle, phase-change heat transfers, and thermal resistance of each loop are compared. With effusion, the evident pressured-drop reduction across the evaporator has led to the decreased boiling temperature and the shrunk sub-cooling region in the evaporator to promote the PTL performance. The merit index that assesses the reductions of loop thermal resistance and total pumping power consumption affirms the considerable thermal performance improvement by the internal effusion in evaporator. Relative to the PTL without effusion, the loop thermal resistance is reduced by 3–32% with the coefficient of performance raised by 14–207%.

A numerical study of battery thermal management system with square spiral ring-shaped liquid cooling plate

The battery thermal management system is critical to the operating safety of power batteries. To alleviate the temperature gradient effect caused by the high local temperature of the battery, a centrally dispersed square-spiral-ring (SSR) mini-channel liquid cooling plate is designed for power batteries in this study. Through the simplification of the battery model, this liquid cooling plate battery thermal management system is investigated numerically. The effects of the number of SSR channel laps, channel width, channel bend radius and inlet mass flow rate on the temperature characteristics of the battery and coolant pressure drop are investigated. The results indicate that increasing the SSR channel laps and narrowing the channel width have a beneficial role in improving the battery and liquid cooling plate temperature distribution. The maximum battery temperature can be significantly dropped and the uniformity of battery temperature distribution can be considerably improved by enhancing the inlet mass flow rate. Moreover, additional branch channels could further improve the uniformity of the temperature distribution and the gradient effect of the battery. The maximum temperature decreases to 33.63 °C and the maximum temperature difference reduces to 6.45 °C during the 2C discharge process at a temperature of 25 °C. Furthermore, the SSR liquid cooling plate with a 5 mm-wide branch channel enables lower maximum battery temperatures and better temperature uniformity with lower pump power consumption than the existing serpentine plate. All these results and evidence provide an option for the development of novel mini-channel liquid cooling plates for battery thermal management.

Topology optimization of laminated-sheet microchannel heat sinks based on a pseudo-three-dimensional method

Laminated-sheet microchannel heat sinks (LS-MHSs) have shown enormous potential in the thermal management of integrated chips due to their advantages of easy integration, high surface-to-volume ratio and high heat transfer efficiency. In this paper, a five-layer pseudo-3D (P3D) conjugated heat transfer model of the double-layer microchannel heat sink (DL-MHS) was established, and topology optimization (TO) was applied for optimal design of the DL-MHS. The effects of different inlet pressures and lamination methods on the optimal design were discussed, and then, the optimization results were compared with those obtained for a single-layer microchannel heat sink (SL-MHS) and conventional parallel microchannel heat sink (CP-MHS). A full-scale 3D conjugate heat transfer numerical model was also built to investigate the heat transfer and fluid flow performance of the topology optimized microchannel heat sink. The results showed that the topology optimized microchannel heat sink can enhance heat transfer and show a higher heat transfer and comprehensive performance compared to the conventional parallel microchannel heat sink. Under the same pumping power consumption, the topology optimization of the DL-MHS with parallel flow obtains the best heat transfer performance, which is 2.04 times that of the CP-MHSs and 1.09 times that of the SL-MHS. Under the same pumping power consumption, the topology optimization of the DL-MHS with counter flow achieves the best temperature uniformity and its maximum temperature difference is 5.0–16.9 K lower than that of the CP-MHSs and 1.6–3.4 K lower than that of the SL-MHS.

Research on pumping laws of different-shaped Roots rotors for multi-stage vacuum pump design

Multi-stage Roots dry vacuum pumps are widely used in the semiconductor industry, metallurgy, pharmaceuticals, solar photovoltaic, thin film equipment, and other such fields. There are many combinations of rotors from the inlet to the exhaust of the multi-stage Roots vacuum pump. Depending on the application process of the multi-stage Roots vacuum pump, different rotation and self-combination designs are required. Currently, the pumping characteristics of different rotor types of the multi-stage Roots dry vacuum pump are not clear, and the combined design of the multi-stage pump rotor cannot be supported. In order to realize the applicability analysis of different rotors in different pressure ranges, a vacuum pump test platform and an adjustable rotor Roots experimental pump were designed. The pumping performance and power consumption of two-lobe Roots rotors, three-lobe Roots rotors and five-lobe Roots rotors in different pressure ranges were tested in experiments, and the internal flow conditions of multi-stage pump exhaust stages were numerically simulated. The results demonstrate that considering the ultimate performance and power consumption, the two-lobe Roots rotors and the three-lobe Roots rotors are more suitable for the exhaust pressure range of 1–10,000 Pa. With the increase of the exhaust pressure, the pumping performance of the three-lobe Roots rotors begins to gradually improve, and the pumping performance has obvious advantages. When the exhaust pressure exceeds 50,000 Pa, the advantages of the five-lobe Roots rotors gradually become obvious. The five-lobe Roots rotors can better handle the process of direct exhaust to atmosphere. The research methods and conclusions adopted in this paper can provide a reference for the design of the rotor combination scheme of the multi-stage Roots dry vacuum pump.

The heat transfer enhancement of the converging-diverging tube in the latent heat thermal energy storage unit: Melting performance and evaluation

Latent heat thermal energy storage (LHTES) has emerged as a promising approach to settle the intermittent and fluctuant of renewable energy but heat transfer enhancement is necessary due to the low thermal conductivity of the phase change material (PCM). This study numerically investigated the heat transfer enhancement effect of the typically converging-diverging tubes (CDTs) inside a shell-and-tube LHTES unit. The evolution of melting behavior was analyzed to describe the heat transfer enhancement mechanism of the CDT. Based on the enhancement effect and pump power consumption associated with the CDT, a modified performance evaluation criterion (PEC) was established to evaluate the feasibility of current designs. The arrangement of CDTs was found to significantly improve the heat transfer performance of LHTES. The triangle CDT exhibited the maximum melting time reduction of 20.77%. The heat transfer enhancement effect of CDT was attributed to the enhanced natural convection of PCM and forced convection of heat transfer fluid. The analysis of the evaluation ensures the feasibility of the new criterion and its specific application field. Moreover, it was worth to note that the triangle CDT achieved the best cost performance of 0.363 ω, where ω represented the return factor.

Research on Gravity Energy Saving Reconstruction Technology of Circulating Cooling Water in Mechanical Ventilation Cooling Tower of a Steel Plant

There is a height drop in the rain area of the circulating cooling water in mechanical ventilation circulating cooling towers, resulting in the ineffective use of gravitational potential energy. High-level water collection is an effective way to reduce the energy consumption of the cooling tower. Based on this, aiming to solve the gravity energy waste problem of circulating water in the cooling tower of a steel plant, this paper innovatively puts forward the high-level water tank to utilize the energy-saving transformation technology of turbine power generation and pump power saving. Additionally, this paper explores the energy-saving effects of the two methods under different height drops. The results show that the maximum utilizable rain area height of the cooling tower is 5 m, while the annual electric energy output of turbine technology can reach 4.704 million kW·h. The high water collection technology can reduce pump power consumption and save up to 7.35 million kW·h per year of electric energy, maintaining a more significant energy-saving ability compared with the turbine power generation technology. In terms of performance, the design of a high-level water tank is to help eliminate rain areas and improve the heat exchange efficiency of water and gas, so that the water temperature of the outgoing tower is 0.13 °C lower than that of the conventional cooling tower. Meanwhile, the ventilation resistance in the rain area is weakened, the resistance coefficient can be reduced by about 40–50%, and the noise can be reduced by about 10 dB (A) under the action of the water collection device. According to the economic evaluation, the total cost of turbine power generation technology is 0.563 million dollars and the total cost of high-level water collection technology is 0.446 million dollars. The cost can be realized within two years, but the high-level water collection technology avoids additional pump maintenance costs and has better economy. This study provides a theoretical basis for the transformation and optimization design of mechanical ventilation cooling towers, and has important reference value.

An integrated simulation of intermittent heating of multi-zone buildings by heat-pump heating systems with different terminal types

Intermittent heating has been considered to be an effective way to achieve energy savings compared with continuous heating. However, recent studies have found that actual energy savings from intermittent heating vary greatly, depending on actual building conditions, terminals and heating supply systems. For multi-zone buildings adopting heat pumps with specific terminals, a comprehensive analysis of energy savings resulting from intermittent heating still needs to be done. In the present study, an integrated dynamic model is developed by considering the interaction of thermal processes among building envelopes, terminals, and heat pumps. Its reliability is verified in field tests, and a better accuracy was achieved when considering the radiant heat ratio of terminals. On this basis, the model together with a source and terminal control strategy is applied to simulate the thermal behavior of heat pump heating systems for buildings under various conditions. The effect of different terminals and building envelopes on room temperature variation and energy utilization by intermittent heating is analyzed. The simulation results and practical projects indicate that heat pump power consumption under intermittent heating may be lower, close to or even higher than that under continuous heating. The factors that affect the efficient of intermittent heating, including building and system thermal inertia, heat pump operation COP, the radiant heat ratio of terminals, need to be systematically considered. Specifically, fan-coil heating systems could use 16.48% less energy, while radiant floor heating systems consume more energy under intermittent heating. Heat pumps under continuous heating are more efficient in buildings with radiative heating systems and heavy envelopes.

Safe-efficient operation strategies for integrated system of photovoltaic and proton exchange membrane electrolysis cells

Proton exchange membrane electrolysis cells (PEMEC) can be utilized to produce hydrogen using renewable energy. In this paper, photovoltaic (PV) integrated with PEMEC is developed for hydrogen production. Based on the operation characteristics of PV and PEMEC, two operation strategies (Strategy 1 and Strategy 2) are proposed to regulate membrane temperature lower than 353.15 K under different solar irradiations. For Strategy 1, the water flow rate is firstly increased and then the inlet water temperature is reduced in the morning with increasing irradiation; and only increasing the inlet water temperature in the afternoon. While for Strategy 2, only reducing the inlet water temperature is adopted in the morning, and increasing the inlet water temperature in the afternoon. Results show that Strategy 1 outperforms Strategy 2 in terms of higher energy efficiency of 5.38% and exergy efficiency of 5.46%. However, the specific energy consumption is higher with Strategy 1 owing to higher pump power consumption, which is 6.15 kWh/Nm3.

Improving energy efficiency of ground thermal energy systems by reducing drag inside pipes

AbstractAt specified depths, ground temperature remains almost constant at 15°C, above atmospheric temperatures in winter and below those in summer. Ground thermal energy systems technology circulates water or brine through a heat‐collection tube buried underground and uses the ground thermal energy for air conditioning. However, depending on the facility, the total length of the heat‐collection tube can be several hundred meters. As a result, the pump can require significant electric power. In this study, we adopted a drag‐reduction technique using a cationic surfactant and a counter‐ion system. The optimal addition conditions of additives were investigated with a laboratory‐grade device. We also investigated corrosion inhibitors that do not interfere with the drag‐reduction effect. According to demonstration tests using practical ground thermal energy systems at two locations in Japan, we found that pump power consumption could be reduced by 10%–20% with suitable additive conditions.

Experimental study on heat transfer performance of high-power spray cooling system based on multi-factor orthogonal test

The traditional cooling system employed in loaders lacks the capability to adjust the fan speed based on the working medium's temperature, resulting in significant power waste. This study introduces a high-power spray cooling system as a solution to this issue. A dedicated spray cooling experimental setup was designed and constructed, and the influence of different factors on the heat transfer performance of the system was studied through multi-factor orthogonal tests with the heat transfer power and energy consumption ratio as evaluation indexes. The results of range and variance analysis demonstrate that the cold water flow rate exerts a substantial impact on both the system's heat transfer power and pump power consumption. Additionally, increasing the nozzle incidence angle can enhance the system's energy consumption ratio. Under the optimal combination of heat transfer power factors, the constructed spray cooling system can achieve a heat dissipation of 44.526 kW at a pump power consumption of 1.184 kW, which meets the heat dissipation requirements of the engine coolant and verifies the feasibility of the proposed scheme. Furthermore, a multiple linear regression model for the power consumption ratio is provided. This investigation yields novel insights for augmenting the performance of loader cooling systems.

Thermodynamic investigation on low GWP drop‐in alternatives to HFC‐245fa in ejector refrigeration cycle for air condition application

AbstractThe ejector refrigeration cycle (ERC) with HFC‐245fa can achieve high efficiency and reliability for air conditioning applications. However, because of its high global warming potential (GWP), HFC‐245fa needed to be phased out according to recent relative regulations. In this study, four promising alternatives to HFC‐245fa were investigated and evaluated, including HC‐600, HCFO‐1233zd(E), HFO‐1336mzz(Z), and HCFO‐1224 yd(Z). Besides their low GWP, these alternatives also have similar vapor pressure curves to HFC‐245fa, which represents a possibility for refrigerant drop‐in replacement in ERC. Thermodynamic real gas modeling of the ERC was adopted in this study for more accurate results, and a critical performance evaluation and comparison with those candidates in ERC were carried out. The results indicate that HCFO‐1233zd(E) and HCFO‐1224 yd(Z) are outstanding candidates for ERC according to the higher coefficient of performance, entrainment ratio, exergy efficiency, and lower pump power consumption, and the COP relative differences of these two refrigerants would reach 5.5% and 4.6%. HFO‐1336mzz(Z) consumes 33% less power at the pump than HFC‐245fa under the same conditions and refrigeration capacity. Minimal pump power consumption is its advantage. Although HC‐600 is prominent, with the largest coefficient of performance and entrainment ratio, its flammability is not conducive to its popularization. Machine learning is available to predict the performance of ejectors employing different refrigerants. This paper helps to properly select refrigerants for ERC and to pre‐evaluate the refrigerants' application under different working conditions.

수열 이용 히트펌프 시스템의 열원 측 배관 설계 변수에 따른 동력소비량 변화 분석

The power consumption of pumps in a hydrothermal heat pump system is important from environmental and economic points of view. In this study, an office building and a hydrothermal heat pump system were modeled by the TRNSYS 18 program, and building load and energy consumption were simulated. The variation in pump power consumption was analyzed according to changes in the design parameters for heat source-side piping in the heat pump system. The system consisted of a heat pump, pumps, heat exchangers, and a fan coil unit. The flow rate and power consumption of the pumps and the fan were calculated by the system operating time to satisfy the building load. A simulation was performed by changing the horizontal distance to the hydrothermal source from 200 m to 1000m, vertical height differences from 2 m to 10 m, and pipe diameters from 0.1 m to 0.3 m. The intake pump (Pump A) power consumption ratio to total power consumption increased from 6.5% to 11.7% with increases in the distance to the hydrothermal source. The simulation results showed that the pipe diameter had a great influence on the power consumption of the pump.