Systemic Pressure Research Articles

Experimental investigation on heat transfer characteristics of a novel hypervapotron channel for divertor target in nuclear fusion reactors

In the further development of nuclear fusion energy, managing the high heat flux on a divertor target remains a significant issue. To address this, the development of innovative cooling channels capable of efficiently managing high heat loads is essential. Among various cooling techniques, the hypervapotron (HV) method stands out for its exceptional heat transfer capabilities. This study undertakes an in-depth analysis of a novel HV cooling channel, evaluating its heat transfer performance via an electron beam high heat flux testing system. The focus was on subcooled flow boiling, observing that the novel HV channel displayed varied flow patterns with increasing heat flux. Additionally, a comparative investigation was conducted to assess the heat transfer efficiency of this novel HV channel against traditional ITER-like HV channel and smooth channel. The analysis incorporated various system parameters, such as mass flow rate and system pressure, to understand their effects on heat transfer. To effectively predict the heat transfer performance of the novel HV channel, efforts have been made to evaluate existing and develop new heat transfer correlations for the channel. Furthermore, Artificial Neural Networks (ANNs) have also been utilized as a crucial approach in this predictive endeavor. The outcomes of this study hold significant implications for understanding and optimizing the design of cooling channels for divertor target in nuclear fusion reactors.

LQTI boost pressure and EGR rate control of a diesel air charge system with eBoost assistance

Turbocharged diesel engines often suffer significant response delay due to so-called turbo-lag, especially engines with large displacement. For this reason, many technologies have been developed to reduce turbo-lag. This paper develops a coordinated control strategy for a diesel engine equipped with an eBoost (electrical compressor) system to significantly reduce turbo-lag. A multiple-input and multiple-output (MIMO) Linear Quadratic Tracking with Integral (LQTI) control strategy, along with its scheduling logic, is developed for the Ford 6.7 L 8-cylinder diesel engine equipped with a variable geometry turbocharger (VGT), exhaust gas recirculation (EGR), and added eBoost along with a bypass valve. Note that the existing production engine does not have an eBoost and bypass valve. Multiple model-based LQTI controllers were designed at different engine operational conditions based on the associated linearized models, and the control outputs are scheduled based upon the engine load condition and bypass valve position. The developed control strategy is validated in both simulation and experimental studies, and the test results show a reduction in engine response time by up to 81.36% in terms of reaching target intake manifold (boost) pressure following a load step-up, compared with the production configuration (without eBoost and bypass valve) with no significant impact on NOx emissions.

Uncertainty calculation of thermal hydraulic simulation of DEC-A accident scenario at VVER-1000 NPP using CIAU method

All thermal hydraulic best estimate simulations of transient scenarios at Nuclear Power Plants (NPPs) are subject to uncertainties. One method to evaluate those uncertainties is implemented by the ”Code with the capability of Internal Assessment of Uncertainty” (CIAU-Code), which calculates the uncertainty for the parameters primary system mass, primary system pressure and hot rod temperature by accuracy extrapolation.The present work now presents an extended use of the CIAU method, by deriving the uncertainty of the parameter iodine-131 release to the environment. For the analysis, a steam generator hot header break with the assumption of a stuck open safety relief valve (BRU-A) at the first opening at the VVER-1000 reactor was selected. Such transient constitutes a design extension condition A (DEC-A), characterized by multiple failures of safety systems but with the reactor core remaining intact. The thermal hydraulic best estimate simulation was conducted with RELAP5-3D. Additionally, the Iodine Spiking (IS) phenomenon for the examined accident scenario was simulated using two different empirical IS models (NRC IS Model and BOKU University IS Model). To allow the application of the CIAU method for the IS calculation a theoretical derivation is provided.The results show that for the selected DEC-A scenario a high uncertainty range has to be expected. The analysis allows a conservative estimation of the risk expected in the event of the examined transient sequence.

Hydrostatic pressure mediates epithelial-mesenchymal transition of cholangiocytes through RhoA/ROCK and TGF-β/smad pathways.

Biomechanical cue within the tissue microenvironment is known to play a critical role in regulating cell behaviors and maintaining tissue homeostasis. As hydrostatic pressure often increases in biliary system under pathological states, we investigated the effect of the moderate elevation of the hydrostatic pressure on biliary epithelial cells, especially on the epithelial-mesenchymal transition (EMT). Human intrahepatic biliary epithelial cells were loaded to hydrostatic pressure using a commercial device. We found that loading the cells to 50 mmHg hydrostatic pressure induced obvious morphological changes and significantly upregulated vimentin, ZEB1, and pSmad2/3, fibronectin, and collagen 1α. All changes induced by hydrostatic pressure loading were effectively mitigated by either ROCK inhibitor (Y-27632) or ALK5 inhibitor (SB-431542). Our in vitro experimental data suggests that hydrostatic pressure loading induces EMT of cholangiocytes through RhoA/ROCK and TGF-β/Smad pathways. Elevated hydrostatic pressure in biliary duct system under pathological states may promote the biliary epithelial cells shifting to profibrotic and mesenchymal characteristics.

Effects of new-type urbanization on resource pressure: Evidence from a water-energy-food system perspective in China

To address the resource and environmental challenges posed by rapid urbanization, China has devised and executed the strategy of new-type urbanization (NU). This study aims to discuss the effects of NU on resource pressure in view of the water-energy-food (WEF) system. Taking 30 provinces in China from 2006 to 2020 as samples, this paper firstly establishes a comprehensive evaluation indicator system of NU from the population, economic, spatial, social and eco-environmental dimensions, and assesses the level of NU using the entropy weight method. Secondly, this paper uses the gray water footprint as a measurement indicator, innovatively integrating water quality into the WEF system for assessing WEF system pressure (WEFSP). Finally, the impact of NU on WEFSP is explored based on the panel fixed effects model. The findings revealed: (1) There is an inverted “U-shaped” relationship between NU and WEFSP, and China's current level of NU has exceeded the Environmental Kuznets Curve (EKC) threshold. (2) The impact of NU on WEFSP exhibits significant regional heterogeneity, with a significant impact in the eastern region. (3) NU consistently exacerbates regional water stress when water quality is considered, indicating that sustainable urban water management practices are essential. (4) The subdimensions of NU indicate that population and social urbanization are important factors that exacerbate the WEFSP, while economic and spatial urbanization reduce the WEFSP. The research results help to clarify the impact of NU on the WEFSP and provide a reference for the timely adjustment and optimization of NU policies to achieve effective resource management and regional sustainable development.

WNK kinase is a vasoactive chloride sensor in endothelial cells

Endothelial cells (ECs) line the wall of blood vessels and regulate arterial contractility to tune regional organ blood flow and systemic pressure. Chloride (Cl-) is the most abundant anion in ECs and the Cl- sensitive With-No-Lysine (WNK) kinase is expressed in this cell type. Whether intracellular Cl- signaling and WNK kinase regulate EC function to alter arterial contractility is unclear. Here, we tested the hypothesis that intracellular Cl- signaling in ECs regulates arterial contractility and examined the signaling mechanisms involved, including the participation of WNK kinase. Our data obtained using two-photon microscopy and cell-specific inducible knockout mice indicated that acetylcholine, a prototypical vasodilator, stimulated a rapid reduction in intracellular Cl- concentration ([Cl-]i) due to the activation of TMEM16A, a Cl- channel, in ECs of resistance-size arteries. TMEM16A channel-mediated Cl- signaling activated WNK kinase, which phosphorylated its substrate proteins SPAK and OSR1 in ECs. OSR1 potentiated transient receptor potential vanilloid 4 (TRPV4) currents in a kinase-dependent manner and required a conserved binding motif located in the channel C terminus. Intracellular Ca2+ signaling was measured in four dimensions in ECs using a high-speed lightsheet microscope. WNK kinase-dependent activation of TRPV4 channels increased local intracellular Ca2+ signaling in ECs and produced vasodilation. In summary, we show that TMEM16A channel activation reduces [Cl-]i, which activates WNK kinase in ECs. WNK kinase phosphorylates OSR1 which then stimulates TRPV4 channels to produce vasodilation. Thus, TMEM16A channels regulate intracellular Cl- signaling and WNK kinase activity in ECs to control arterial contractility.

Heave in the Soil due to Driving Pile Foundations

GIS 150 KV Tambak Lorok III Semarang is a coastal area, stabilization is carried out with piles to reduce land subsidence in the area. In the piling process the soil grains are forced vertically and laterally when the pile foundation is driven into the ground, thus increasing the water pressure in the soil pore system. Nearby buildings will be affected and may suffer damage. The pile driving location for the GIS 150 KV Tambak Lorok III Semarang project is adjacent to other structures. So, the amount of land that needs to be cleared around the project must be calculated. This study uses methodology that makes theoretical predictions about the magnitude of heave caused by piles. Subsequently, vertical ground movement measurements made using the Finite Element Method (Plaxis Program) were compared with the theoretical predictions. Pile depth variations of 45 and 50 meters were performed in the plaxis analysis. In conclusion, the results of the two approaches will be contrasted. In the GIS 150 KV Tambak Lorok III Semarang project, soldier piles with a diameter of about 600 mm were driven 45 meters deep into the ground with hydraulic jacks. The theory led to the conclusion that the heave values for the effect of piling at -45 m depth and at -50 m depth were 0.1285 m and 0.1284 m, respectively. Based on Plaxis pile measurements at a depth of 45 meters, the vertical soil movement value was 5.80 cm, while 4.90 cm was recorded for a depth of 50 meters.

Robust pressure prediction of oil and gas pipeline networks based on equipment embedding neural network

Currently, extensive pipeline networks are developed in response to the demands of the oil and gas industry. The accurate estimation of the hydraulic condition of pipeline networks holds significant importance in the fields of pipeline design and safety management. Nevertheless, predicting the pressure of oil and gas pipeline networks with different equipment and structures remains challenging. To meet this challenge, a novel pressure prediction model for the oil and gas pipeline networks based on the equipment embedding neural network (EENN) is proposed in this study. The proposed model embeds different equipment models into the neural network model. The neural network in this model is used to focus on learning the connection characteristics of the pipeline network to achieve higher prediction accuracy. The present study first explores different embedding combinations of the EENN model to estimate the pressure in an oil pipeline network system that involves a non-isothermal batch transportation process. Then, the trained model is applied to predict the pressure in a gas pipeline network. The optimal EENN exhibits an average prediction error of 18.5% for oil pipelines and 0.36% for gas pipelines, which is lower than 20.8% and 3.57% under the neural network. The findings of this study demonstrate the efficacy of the proposed EENN in accurately forecasting pressures in diverse oil and gas pipeline networks by reducing the complexity of the learning process.

Analysis of a refrigeration system using carbon nanotubes (CNTs) lubricant and a combination of R290/R600 refrigerants

A combination of R290/R600 refrigerants with low global warming and zero ozone-depleting potential refrigerant was tested with a based lubricant and CNTs nanolubricant in a refrigeration system to improve its performance efficiency and minimise the environmental impact of refrigerants and energy demand by refrigeration systems. CNTs-nanolubricant, an alternative lubricant for the refrigeration system, was made by dispersing CNTs in the based lubricant. By connecting measuring devices at each system component, temperatures and pressures were determined. The experiment’s measured outputs were used to determine the system’s performance. When compared to a 290/600 in the based lubricant, CNTs nanolubricant showed a reduction in work input ranging from 39.8%, a shorter pulldown time, a lower evaporator temperature, an increased coefficient of performance (COP), and a higher cooling capacity of 9.1%. Therefore, the lubricant made of carbon nanotubes (CNTs) presents a viable substitute for based lubricant in a vapour compression system.

The effect of solid nitrogen on nucleate boiling heat transfer in a slush nitrogen pool

The nucleate boiling heat transfer in a slush nitrogen pool has been studied across a heat-flux range from 5 to 400 kW/m2 and a system pressure range from 12.5 kPa (triple point pressure) to 101 kPa (atmospheric pressure). The effect of solid nitrogen on the heat transfer process was found to vary with the heat flux and the pressure. Experimental results reveal that the nucleate boiling heat transfer coefficient (HTC) of slush nitrogen is higher than that of subcooled liquid nitrogen at the low heat flux, which can be attributed to the fact that the solid nitrogen particles (with their latent heat of melting) absorb heat in the thermal boundary layer and form a sharper temperature gradient near the boiling surface. However, at the high heat flux, the HTC of slush nitrogen is lower than that of subcooled liquid nitrogen, which can be attributed to the invasion and inhibition occurring between the solid nitrogen particles and the bubbles during boiling, leading to the accumulation of vapor phase with low thermal conductivity on the boiling surface, thereby the heat transfer will be suppressed. As a result, a dual effect for the nucleate boiling heat transfer in slush nitrogen can be observed. Furthermore, the critical heat flux (CHF) of slush nitrogen is obtained and compared with the CHF of subcooled liquid nitrogen. According to the CHF model, the bubble period is the dominant parameter in determining the CHF. A calibrated CHF correlation for slush nitrogen is developed based on the hypothesis that the bubble period is prolonged as the effective viscosity of slush nitrogen increases with the solid volume fraction. The CHF values of slush nitrogen with the solid volume fraction of 10%, 20% and 30% are 0.96, 0.91 and 0.84 times those of subcooled liquid nitrogen, respectively, at the pressures higher than 50 kPa. Consequently, the solid volume fraction of slush nitrogen and the degree of subcooling of subcooled liquid nitrogen are found to have opposite effects on CHF.

Dynamic performance prediction and experimental analysis of wet clutch actuator considering thermal flow characteristics

The hydraulic actuator system (HAS) for wet clutches in heavy-duty vehicle transmissions is required to have a fast response and high precision in the pressure regulation procedure. Conventional pressure control valves for HAS are almost slide spool structures, which perform a large flow force at a high flow rate. An open-center spool structure is designed and developed in this paper, which is a combination of a traditional slide spool and a valve sleeve. It has an orifice-groove combination throttling orifice, which can take into account the large through-flow capacity and small flow force. Firstly, to deeply understand the mechanism of pressure variation in the clutch chamber, a high-fidelity dynamic characteristic mathematical model of HAS considering the oil temperature is proposed. Secondly, the functional relationship between the oil temperature on the medium physical property parameters and the orifice thermal flow parameters in the model is deduced in detail. An experimental bench to measure the pressure valve dynamic performance and actuator pressure regulation characteristics in a wide temperature domain is then designed and implemented to validate the accuracy of the simulation model. Finally, the mechanisms of oil temperature and system pressure on pressure impact and pressure response are quantitatively analyzed in association with a supervised learning algorithm. The feasible domains of the two adjustable variables are also explored. This study provides a new perspective on dynamic control and energy saving of HAS pressure valves and a new method for the prediction of HAS performance under complicated operating conditions.

Thermodynamic modelling, testing and sensitive analysis of a directly pressurized hydrogen refuelling process with a compressor

This paper presents the development of a thermodynamic model for the hydrogen refuelling station (HRS) to simulate the process of refuelling, which involves the transfer of hydrogen gas from a high-pressure storage tank to the onboard tank of a fuel cell electric vehicle (FCEV). This model encompasses the fundamental elements of an HRS, which consists of a storage tank, compressor, piping system, heat exchanger, and an on-board vehicle tank. The model is implemented and validated using experimental data from SAE J2601. Various simulations are conducted to assess the impact of the Joule-Thomson effect and compression on the temperature of hydrogen flow, specifically focusing on an average pressure rate of 18 MPa/min. Furthermore, a comprehensive analysis is conducted to examine the impact of pressure variations in the storage tank (10–90 MPa) and the initial pressure within the vehicle tank (5–35 MPa), as well as variations in ambient temperature (0–40 °C). The study revealed that the energy consumption in the cooling system surpasses the average power consumption in the more advantageous scenario of 60 MPa by a range of 36% to over 220% when the pressure in the storage system drops below 30 MPa. Furthermore, it was noted that the impact of ambient temperature is comparatively less significant when compared to the initial pressure of the vehicle's tank. The impact of an ambient temperature change of 10 °C on the final temperature of a hydrogen vehicle is found to be approximately 2 °C. Similarly, a variation in the initial vehicle pressure of 10 MPa results in a modification of the final hydrogen vehicle temperature by approximately 8.5 °C.

Experimental study on single- to two-phase flow and heat transfer of water in a small tube

Experimental investigation on flow boiling heat transfer in a small tube under high system pressure has been conducted in this study. The test-section is constructed with a 316L stainless steel tube. The inner diameter and heated length of the test-section are 5 mm and 930 mm, respectively. The working fluid is deionized water. The operating conditions of the experiments are as follows, the mass flux from 548 to 978 kg/(m2·s), the wall heat flux from 136 to 238 kW/m2, and the system pressure from 1.0 to 2.9 MPa. The experimental results showed that the inlet subcooling mainly affects the onset of nucleate boiling, but its impact on the heat transfer coefficient at the same vapor quality is almost negligible. The heat transfer coefficient increases with the increase of mass flux and wall heat flux, especially in the region where xe < 0.02. The average heat transfer coefficient is higher under high system pressure owing to the variation of the thermophysical properties. Additionally, the existing flow and heat transfer correlations cannot predict the flow boiling heat transfer coefficient and frictional pressure drop in the experiments accurately enough. Therefore, the new flow and heat transfer correlations are developed based on the experimental data in this paper, and the mean absolute deviation of the flow boiling heat transfer correlation and frictional pressure drop correlation are 13.3% and 12.1%, respectively.

Experience of Morphologic Left Ventricle Training in Congenitally Corrected Transposition of the Great Arteries in Children: Evaluation of the Operation Results

The aim. To evaluate the efficacy of morphologic left ventricle (mLV) training through pulmonary artery banding (PAB) in pediatric patients with congenitally corrected transposition of the great arteries.&#x0D; Materials and methods. From 2003 to 2023, 12 patients underwent PAB for mLV training at the Ukrainian Children`s Cardiac Center. The mean age of the patients was 30.3 ± 25.1 months, the mean weight was 11.6 ± 5.2 kg. Hemodynamic parameters were assessed to determine the size of the band applied to the pulmonary artery (PA) trunk during the operation. Intraoperative transesophageal echocardiography was performed in 6 patients. Transthoracic echocardiography (TTE) was performed in the early postoperative period. In the remote period, all the patients underwent TTE and X-ray angiography.&#x0D; Results. During PAB, the mLV pressure averaged 58 ± 12.6% (from 40% to 80%) of the systemic arterial pressure. PAB dilatation was required for one patient in the early postoperative period (postoperative day 2) because of significant hemodynamic changes. In the early postoperative period, the maximum gradient across PA measured by TTE averaged 39.3 ± 10.0 mm Hg (from 25 to 60 mm Hg). There was no hospital mortality.&#x0D; The follow-up period averaged 47.2 ± 26.0 months (8 to 113 months). In the long-term observation period, 2 patients (16.6%) died, one 8 months and the other 5 years after the operation. The double switch operation was performed in 6 patients, on average, 48.2 ± 6.9 months after PAB. According to angiography, the mLV pressure before the double switch operation was 90.2 ± 11.6% of that in the systemic right ventricle. The end-diastolic pressure in the mLV averaged 14 ± 4.1 mm Hg. The peak pressure gradient across the PA measured by echo was 81.3 ± 28.8 mm Hg. The mLV mass index averaged 62.9 ± 8.8 g/m2, the mLV ejection fraction averaged 61.2 ± 2.9%. Overall radiographic and echocardiographic data in these patients indicated that mLV is trained and capable of performing the role of a systemic ventricle after anatomical correction.&#x0D; Conclusions. PA banding as a method of mLV training can be used in patients with congenitally corrected transposition of the great arteries with intact ventricular septum, restrictive ventricular septal defects and severe tricuspid regurgitation.&#x0D; To evaluate the effectiveness of PAB for mLV training, a multimodal diagnostic approach is used, including non-invasive and invasive methods such as TTE, transesophageal echocardiography, and cardiac catheterization. The optimal age for PAB in patients of this group for the purpose of training the LV was on average 2-2.5 years.

Optimizing neural network algorithms for submerged membrane bioreactor: A comparative study of OVAT and RSM hyperparameter optimization techniques.

Hyperparameter tuning is an important process to maximize the performance of any neural network model. This present study proposed the factorial design of experiment for screening and response surface methodology to optimize the hyperparameter of two artificial neural network algorithms. Feed-forward neural network (FFNN) and radial basis function neural network (RBFNN) are applied to predict the permeate flux of palm oil mill effluent. Permeate pump and transmembrane pressure of the submerge membrane bioreactor system are the input variables. Six hyperparameters of the FFNN model including four numerical factors (neuron numbers, learning rate, momentum, and epoch numbers) and two categorical factors (training and activation function) are used in hyperparameter optimization. RBFNN includes two numerical factors such as a number of neurons and spreads. The conventional method (one-variable-at-a-time) is compared in terms of optimization processing time and the accuracy of the model. The result indicates that the optimal hyperparameters obtained by the proposed approach produce good accuracy with a smaller generalization error. The simulation results show an improvement of more than 65% of training performance, with less repetition and processing time. This proposed methodology can be utilized for any type of neural network application to find the optimum levels of different parameters.

Feasibility study on improving the performance of the kitchen exhaust system by integrating a supercharging fan

Connecting a supercharging fan (SF) in series with the range hood is a practice way to better discharge the harmful oil fumes in residential kitchens, but a poor match SF may fail to help exhaust and even cause additional noise issues. This study aims to clarify how the SF rotation speed affects the operation of the existing range hood and explore the possible noise advantages of the series exhaust system. The computational fluid dynamics method was used to simulate the aerodynamic performance and internal flow of different exhaust systems. Analysis revealed that the system's exhaust capability can only be improved when the SF rotates fast enough, generating sufficient pressure rise to overcome its own flow resistance. Performance leading over the entire flow range is achieved when the SF rotates at 2500 rpm, where the pressure rise in the actual working range is increased by nearly 40%. These performance enhancements buy a rotational speed reduction of almost 300 rpm for the hood fan when the system's pressure remains unchanged. The airflow in the range hood thus decelerated by 14.5–18.2%, and the undesired reverse flows were also inhibited. The results obtained by full-scale kitchen experiments show that the sound pressure level of the series system was 0–1 dB lower than that of the original range hood in the same flow rate, and this decrement is maximum to 2 dB by inducing sound-absorbing treatment on the SF. This study provides preliminary guidance for integrating an SF in a range hood exhaust system, offering a novel view of its benefits and challenges.

Research on thermal hydraulic characteristics of reflooding process based on core multi-channel model in system analysis code

There are four main stages in PWR Loss of Coolant Accident (LOCA): blowdown, re-irrigation, re-flooding and long-term cooling. The re-flooding stage is a critical phase to avoid core meltdown and achieve long-term cooling. RBHT reflooding experiment was simulated with the RELAP5 and COSINE program respectively.Thermal-hydraulic characteristics in re-flooding phase were analyzed using multi-channel model. Quench time is mainly influenced by system pressure and coolant subcooling. Later quench will result in a higher cladding temperature. Comparatively, the peak cladding temperature is less affected by the power of the heating rod and the re-flooding rate, which fluctuates within 7 %. The higher re-flooding rate allows quenching to occur as fast as possible and improves cooling efficiency. However, higher coolant sub-cooling and re-flooding rates may cause greater thermal stresses on the core and endanger core integrity. Based on the analysis of the re-flooding rate on the peak cladding temperature and quench time, the optimal re-flooding rate interval of 0.099–0.105 m/s was obtained.

Water column-based assays underestimate benthic predation pressure in mid-latitude systems

Water column-based assays underestimate benthic predation pressure in mid-latitude systems

Numerical analysis of pressure variation and gas load effects in the refrigeration system for household refrigerators

Insufficient air evacuation from a refrigeration system prior to refrigerant charging can lead to an increased non-condensable gas concentration, negatively impacting system performance. Despite its critical importance, literature on refrigeration system vacuuming procedures is notably lacking. This study developed numerical methods and constitutive models to assess gas load, validated against measured pressures using experimental setups. The model developed can be extended and applied to a wide range of vacuum systems. Examining the vacuuming process in a household refrigerator, a connected vacuum pump expedited the process, revealing higher pressures in the capillary tube and condenser outlet due to low flow conductance. The rate of pressure increase attributable to the gas load from outgassing and degassing remained below 0.6 %, deemed negligible during vacuum pump operation. A 24-hour simulation post-vacuum pump cessation showcased pressure equalization and subsequent rise due to outgassing and degassing, resulting in a 201 % increase in pressure within the compressor’s internal space connected to the process pipe. The pressure increase in the compressor attributable to outgassing amounted to 140 %, surpassing the 59 % from degassing. Notably, assuming a 3 μm crack in the process pipe led to a continuous increase in refrigerator system pressure over 24 h. Leakage significantly increases the amount of non-condensable gases inside the system, potentially leading to increased energy consumption and deterioration in system performance.

Optimal discharge pressure and performance characteristics of a transcritical CO2 heat pump system with a tri-partite gas cooler for combined space and water heating

The transcritical CO2 heat pump holds promise for achieving carbon neutrality in buildings, primarily due to its high energy efficiency in hot water heating. However, using it for space heating often leads to efficiency losses. A heat pump equipped with a tri-partite gas cooler can address this issue by providing both space heating and hot water while maintaining lower refrigerant temperatures at the gas cooler exit. Nonetheless, there is limited research on the characteristics of a CO2 heat pump system designed for simultaneous space and hot water production. This work fills this gap by analyzing the impacts of operational and system configuration, considering the variation of space heating to hot water production loads. A theoretical model is presented and verified with the experiments. Results show that under the specified conditions, the heat load ratio has minimal influence on the optimal discharge pressure. Increasing the water outlet temperature from 60 °C to 80 °C leads to a nearly 14% decrease in maximum COP, with a corresponding 12.2% increase in the optimal pressure. A 10 K rise in water inlet temperature results in approximately a 21% decline in maximum COP. Evaporation temperature has little impact on the optimal discharge pressure, while maximum COP increases by roughly 63% with a rise in evaporation temperature from -10 °C to 10 °C. Space heating water temperature notably affects the optimal discharge pressure. Integration of an IHX enhances system COP but has marginal impact on the optimal discharge pressure. These findings offer insights for designing and optimizing transcritical CO2 heat pumps for simultaneous space and water heating applications.