Drop In Water Temperature Research Articles

A new method to improve the thermal performance of high-level water collecting cooling tower based on the migration of vortices

This study proposes a novel annular inlet hat structure designed to address internal vortex flow within high-level water collecting cooling towers (HCTs). To investigate the effect mechanism of inlet hat, a three-dimensional numerical model for an HCT equipped with inlet hat was developed, allowing for a comprehensive analysis of the flow and temperature fields, as well as several performance parameters. The results manifest that the inlet hat strengthens the tower thermal performance by migrating the longitudinal vortices from the interior to the exterior and reducing the number of longitudinal vortices induced by crosswinds. The strengthening effect of inlet hat shows minimal variation when its width exceeds 8 m. Under the studied water flow rates, an 8-m inlet hat results in increases in air mass flow rate, water temperature drop, Merkel number, and evaporation rate by a maximum of 4.3 %, 4.2 %, 6.4 %, and 1.5 %, respectively. In terms of crosswinds, the inlet hat operates with optimal efficiency at a direction of 0° and a velocity of 13 m/s, achieving maximum increases in air mass flow rate, water temperature drop, and Merkel number of 23.3 %, 25.4 %, and 33.6 %, respectively. These findings demonstrate the feasibility and practical value of the proposed inlet hat.

Enhancing Solar Water Heater Performance Using Phase Change Materials and Modified Encapsulation Geometry

ABSTRACTSolar energy's abundant availability in India makes it a potential solution to meet increasing energy needs without harming environment. Solar water heating (SWH) systems are effective in converting solar radiation into heat for domestic and industrial applications. However, their inability to provide hot water during nighttime or off‐sunshine hours due to the intermittent nature of solar energy presents a challenge. Thermal energy storage, particularly using phase change materials (PCMs), has emerged as a solution. In this study, spherical ball‐type encapsulated PCM, specifically RT60, was incorporated into a solar water heater tank under variable atmospheric conditions. The PCM stores excess energy during daylight and releases it when the water temperature drops below the PCM's melting point. The results reveal a significant reduction in the temperature drop of water from 4.5°C to 1.4°C when utilizing PCM compared to conventional storage water tanks without PCM. Additionally, energy storage capacity is enhanced by 5.13% with PCM incorporation. Furthermore, modifying the encapsulation geometry to a rectangular shape enhances heat transfer and reduces temperature drop even further to 0.9°C, making it a promising approach to improving SWH system performance. This study highlights the possibility of enhancing encapsulation shape and applying PCM to enhance SWH system performance. The results highlight the possibility of increasing solar thermal systems' energy efficiency and usefulness, which will support sustainable energy sources.

Organic petrographic and geochemical insights into organic matter derived from land plants and marine algae in the Lark Formation, Danish North Sea

Climatic fluctuations from the Eocene to the Miocene highlight the importance of investigating the paleoenvironment of the latest Eocene to the Middle Miocene Lark Formation in the Danish North Sea. This study investigates immature sedimentary organic matter in the Lark Formation using 54 cuttings samples and one core sample collected from seven wells in the eastern North Sea Basin. Organic petrography and molecular geochemistry analyses were performed to determine the variations in the quantity and origin of allochthonous and autochthonous organic matter. Additionally, the study assesses the impact of climate fluctuations on marine productivity in the eastern North Sea Basin and land plant vegetation at the basin margins during the latest Eocene to the Middle Miocene.The organic matter in the Lark Formation originated from mixed sources, primarily land plants, with a secondary contribution from marine algae. This is indicated by the maceral composition and the types and abundance of aliphatic and aromatic hydrocarbon biomarker compounds. Moreover, the presence of diterpenoids (gymnosperm biomarkers) and non-hopanoid triterpenoids (angiosperm biomarkers) reveals that the allochthonous organic matter originated from conifers and angiosperms.Climatic impacts on land plants and marine algae during the latest Eocene to the Middle Miocene are revealed by several parameters: the Averaged Chain Length (ACL) of land plant waxes, the proportion of coniferous contribution (C/(C + A)), and the whole rock volume percentages of huminite, inertinite (H + I, vol%) and liptinite (L, vol%). The shifts to cooler and drier climates highlighted the cold adaptation of onshore conifers and resulted in the input of higher molecular weight waxy components into the sediments. However, under these conditions, reduced precipitation and runoff resulted in lower amounts of terrigenous organic matter supplied to the basin. Additionally, the drop in water temperature and the warm-affinity of local algae assemblage led to reduced marine productivity. Together, these factors contributed to an overall decrease in organic richness. In contrast, during shifts to warmer and more humid climates, the trend reversed. The contribution of conifers to the floral assemblage diminished, but higher amounts of terrigenous organic matter were transported to the basin due to increased precipitation and runoff. This was accompanied by warmer water temperatures, boosting the productivity of organic-walled microplankton in the marine environment and contributing to greater organic richness.

Performance analysis of zeotropic organic Rankine cycle with a vapor-liquid injector

To improve the performance of small-scale organic Rankine cycle (ORC), an ORC with a vapor-liquid injector (IORC) using zeotropic mixture R601a/R245fa as working fluid is proposed. Parametrical investigations of the injector and system are carried out. The research results of injector show pure R601a has the highest injector pressure lift and exergy efficiency. The working fluids with higher temperature glide tend to have lower exergy efficiency. The increase of injector entrainment ratio and injector area ratio decreases pressure lift and exergy efficiency. The research results of system shows that the introduction of the zeotropic working fluid and injector can complement advantages and disadvantages of each other. Taking R601a/R245fa (60 %:40 %) as working fluid, IORC has higher net power than basic ORC (BORC) when pump efficiency is lower than 88 % and hot water temperature drop is less than 51 °C. There exists an injector entrainment ratio which makes net power maximum. Increasing injector area ratio decreases net power. Increasing injector entrainment ratio and decreasing injector area ratio reduce cooling water. Increasing injector entrainment ratio and injector area ratio makes heat exchanger economy worse.

Marine aquaculture spatial planning on market orientation for Pacific oyster in Shandong, China

Accessing the production value is essential to the selection of suitable sites for aquaculture farms. This study employed a Dynamic Energy Budget (DEB) model and used market-oriented indicators, including shell length, flesh weight, condition index and minimum farming duration, to analyze the suitability for Pacific oyster aquaculture in offshore Shandong, China. Chlorophyll a (Chl-a) concentration, Total Suspended Sediment (TSS) concentration, and Sea Surface Temperature (SST) were extracted by remote sensing and used as forcing variables in the bioenergetic model. Four market-oriented indicators and five zones in the study area were chosen to develop a Suitable Market-Aquaculture site-selection model (SMASM) and estimate the oyster farming suitability. The results demonstrated that Sanggou Bay exhibits high potential for Pacific oyster year-round aquaculture. Eastern Laizhou Bay is suitable for the autumn-spring fattening culture of adult oysters. Laoshan Bay and Changshan Islands are suitable for promoting rapid growth in juvenile oysters. The results of our model were consistent with the oyster production value in Shandong, showing an overall increasing trend except for the anomalous value observed in 2019. Sudden drops in water temperature, red tides, and significant increases in turbidity can exert detrimental effects on oyster production, which has been evidenced to be influenced by Super Typhoon Lekima in 2019. Although this study concentrated on a specific geographical region, the model could be applied to other regions to develop market-oriented suitability management for species and environments worldwide.

Numerical simulation and experimental investigation on Phase Change Materials based energy storage system for cooling the water in process industries towards water conservation and environmental sustainability

Water conservation is one of the significant concerns in the industrial sector in cooling processes. Water is lost predominantly in the cooling towers by evaporation, drift, and blowdown. A new Phase Change Material (PCM) based cooling system is proposed as a replacement for cooling towers to eliminate water losses completely. In the current research, the temperature drop of water known as range in the cooling tower is investigated in the proposed system by varying the process parameters such as water velocity, tube materials and tube lenght. In the present study, OM50, an organic PCM with a melting temperature of 500 C is chosen for experimental and numerical analysis as the normal operating temperature of water in the cooling towers is in this range. Based on the experiment, it is observed that the temperature range of water almost remains constant for the melt fraction values of PCM from about 0.1 to 0.8 and taking about 35 % of the total time required for completely melting the PCM. However the cooling range steeply decreases for the melt fraction variation from 0.8 to 1. Hence the designing of PCM based cooling system will be effective for the melting of the PCM from 0.1 to 0.8 leading to constant cooling range of temperature. The experimental results obtained are also validated by CFD simulation using ANSYS 18.1 and the results obtained are in close agreement with each other. The range obtained in the present research is almost in the same range of cooling tower used in the chiller plant presented in the case study. The proposed system may be able to replace cooling towers towards conservation of water and environmental sustainability.

Numerical study on heat and mass transfer performance of a natural draft wet cooling tower based on baffle optimization

In the natural draft wet cooling towers (NDWCTs), the resistance of the packing layer to air and the effect of the circular design of its cross-section, the air reaches the tower center area to overcome the maximum resistance. The air velocity in the center of the tower is low and the heat transfer is poor. To improve the performance of the cooling tower, the optimized design of the cooling tower distribution pipe surface with baffles is firstly investigated. Then, the three-dimensional numerical model of NDWCTs is developed and validated with power plant data. Finally, the effect of plates on cooling tower performance is analyzed through the influence of baffles on the cooling tower air field and combined with the circulating water temperature drop, evaporation, and ventilation. Results show that the air field uniformity inside the cooling tower is effectively improved by adding baffles. The cooling efficiency of the circulating water inside the cooling tower is improved. The air velocity in the packing zone is significantly increased by adding the a1a2 type baffle and the air temperature and circulating water in the central area of the tower decreases significantly and the a1a2 baffles performed best in terms of circulating water temperature drop in the packing zone and were able to significantly improve the cooling effect. The cooling tower with pro-wall baffles can cool the circulating water better than the conventional cooling tower. This study provides ideas for subsequent structural and energy efficiency studies.

Multi-objective optimization of hollow fiber membrane-based water cooler for enhanced cooling performance and energy efficiency

Water-mediated evaporative cooling systems often suffer from cross-contamination, droplet carryover, and high maintenance costs. This study proposes a novel liquid cooling solution, the hollow fiber membrane-based water cooler (HFMWC), to address these issues. The primary innovation of this study lies in the optimization of key design parameters of the countercurrent HFMWC, aligning them with stringent engineering requirements. Two standard working conditions for wet cooling towers are considered. Numerical modeling and response surface methodology are used to develop regression models correlating six key parameters (water velocity, air/water ratio, fiber length, fiber inner diameter, membrane thickness, and packing fraction) with two performance evaluation indexes (outlet water temperature and consumptive electric power ratio). A genetic algorithm-based multi-objective optimization is employed to obtain Pareto fronts, representing optimal trade-offs between the two indexes. Using the ideal point method, relative optimal solutions are identified, resulting in water temperature drops of 7.56 °C and 13.07 °C, with consumptive electric power ratios of 0.0128 kW h/m3 and 0.0138 kW h/m3 for conditions Ⅰ and Ⅱ, respectively. Most solutions achieve the highest energy efficiency rating while satisfying the design temperature difference. The average deviations between optimized and simulated data for the two indexes are 0.88 % and 3.88 %, demonstrating the reliability of the derived optimal solutions for engineering design. These findings not only offer a promising way to overcome the limitations of traditional evaporative cooling systems, but also contribute to the broader field of sustainable and efficient thermal management technologies.

Heat load-carrying capacity of surface water source and its heating load matching characteristics

Meteorological parameter changes not only affect the heat load-carrying capacity of the surface water, but also affect the heat load demand of the building, thus changing the heat load matching between the water source heat pump system and the users. In order to study the climatic adaptation of the heat load-carrying capacity, this paper establishes an analytical model of the water body's heat load-carrying capacity and the building's heat load with the solar radiation intensity, the change of the water body and the heat extraction time as variables. Experimental and simulation studies on the heat load-carrying capacity of lake water were carried out under the winter climate conditions in hot summer and cold winter areas. The results show that increasing the depth or area of the lake can improve the heat load-carrying capacity. Solar radiation is an important factor affecting the temperature of surface water body, the stronger the solar radiation the greater the temperature rise of the water body. Changes in outdoor air temperature have a significant impact on water temperature, and a sudden drop in outdoor air temperature will result in a sharp drop in water temperature. When the water body area was 3000 m2 and 50000 m2, the maximum integrated temperature drop of the water body was 15.0℃ and 9.7℃, which was 2.02 and 4.85 times of the temperature drop of heat extraction, respectively. Reduced heat load-carrying capacity of the surface water body or decreased COP of the heat pump is an important reason why the surface water source heat pump heat supply fails to meet the user's heat demand in winter.

Effect of Long-Term Day/Night Temperature Oscillations on the Overall Performance of Gilthead Seabream (Sparus aurata) Juveniles

Water temperature variations affect fish growth and health, often leading to huge losses in fish production, especially during the cold season. To alleviate this constraint, fish farmers can use a water heating system driven by solar energy during daytime. This action will cause a water temperature drop during the night period, making it important to understand the physiological response of fish exposed to the resulting day/night temperature oscillations. To investigate this scenario, gilthead seabream juveniles (96.3 ± 1.0 g) were exposed to different thermal regimes for 67 days: Tconstant and Tdaily cycles. The latter group was exposed to daily water temperature oscillations between ~19 and 13 °C compared with a constant temperature of ~19 °C for the other experimental group. Temperature fluctuations compromised fish growth efficiency and reduced the proportion of fatty acids in several tissues, with implications for the whole proximate composition. Moreover, temperature oscillations influenced several blood parameters. These results favor the usage of a constant water temperature of ~19 °C for optimal gilthead seabream juvenile production instead of a day/night water temperature oscillating regime. Nevertheless, the type of energy used to warm the water will depend on the operational conditions and/or business strategy of fish farmers.

Improving the performance of indirect evaporative cooler for energy recovery from the perspective of nozzle configuration: A CFD model analysis

As a sustainable cooling technology, indirect evaporative cooling (IEC) has been widely recognized as an effective means of achieving carbon neutrality based on its low energy consumption and high efficiency in central air conditioning (AC) systems of buildings. In contrast to the conventional arrangement, IECs as heat recovery units are often arranged in a diamond shape inside the air handling units (AHUs) of data centers (DCs), an approach that facilitates the flexible use of space and integration within the units in a more compact form. The use of CFD simulations allows an integrated analysis of the coupling of hydrodynamic, thermal and mass properties helps to improve the evaporation performance of IECs. In this study, a 3D simulation model of a diamond-shaped IEC containing the water spray system was developed to compare and analyze the air-water arrangement options in IEC systems currently used in DCs, and the corresponding characteristics are explored from the perspective of CFD techniques to determine the effect of nozzle configurations on the formation and evaporation of water film within the wet channels. Then, parametric analysis of nozzle setup schemes based on performance metrics showed that the nozzle arranged in top-side configuration and paired with the air-water counterflow form had the best performance, with 59.2% and 27.4% improvement in water film coverage area and temperature drop, respectively, over the worst scheme (bottom configuration) at a water supply flow rate of 65 L/s. Finally, the effectiveness of the enhanced approach was simulated and analyzed for hydrophilic and fiber coatings, and it was found that the water film coverage increased by 14.5% and 31.6%, respectively, while the coefficient of performance (COP) increased by 7.4% and 16.1%.

Synergistic optimization of partition water distribution, non-equidistant fillings and dry-wet hybrid rain zone for wet cooling towers

Existing single-zone or two-zone synergistic optimization technologies have limited performance improvements for the large natural draft wet cooling towers (LNDWCTs). To further improve the cooling performance of the LNDWCTs, this study proposes for the first time a three-zone (water-spraying, fillings and rain zones) synergistic optimization method from a global optimization perspective. The 3D numerical calculation model is created and validated. Then, this work investigates emphatically the impact of the different three-zone parameters on the cooling performance, including the partition water distribution radius (R1 = 20 ∼ 60 m), the water distribution percentage in the inner zone (γ=5 ∼ 90 %), the fillings partition radius (R2 = 0 ∼ 65 m), the total coverage area of the split-flow plate (S = 2000 ∼ 2900 m2), the installation angle (θ=0 ∼ 27°), the split-flow plate length (L = 15 ∼ 55 m) and number (n = 3 ∼ 10). The simulation results illustrate that, within the studied range, the water temperature drop, cooling efficiency and Merkel number increase and then decrease with the increasing R1,γ, R2, θ and n, and increase successively with the increasing S and L. The optimized three-zone parameter combination scheme is R1 = 55 m, γ=75 %, R2 = 50 m, S = 2900 m2, θ=6°, L = 55 m and n = 7. Compared to the LNDWCT without any optimization technology, the water temperature drop, cooling efficiency, Merkel number, ventilation and evaporation loss of the cooling tower with optimized three-zone synergistic pattern increase by 0.58 °C, 3.37 %, 0.17, 1480 kg/s and 41.28 kg/s, respectively. This study can lay a theoretical basis for the multi-zone synergistic optimization research of LNDWCTs and provide a reference for the technical modifications and engineering applications.

Modern approaches ensuring rational conditions for continuously cast billet formation in a billet CCM mold.

The development of technology and technology of continuous steel casting actualizes the improvement of the control system of casting processes and diagnostics of the formation of continuously cast billets. The conditions determining the stability of continuous cast billet forming process in billet CCM mold are considered: the correspondence of liquid steel mass entering the mold and the outgoing billet mass; ensuring the specified intensity and uniformity of billet cooling in the mold sleeve; ensuring a rational level of friction in the crystallizer. It is shown that, on the one hand, heat transfer in the mold is largely determined by the correspondence of the billet shrinkage and the internal profile of the mold, but, on the other hand, it is noted that it is impossible to obtain a universal profile that creates optimal conditions for the formation of billets from all grades of steel with arbitrary temperature-speed parameters. Therefore, the concept of a universal crystallizer assumes that rational conditions of heat removal are achieved due to additional influences. The basics of diagnosing of heat exchange processes in the crystallizer are presented, based on the computational processing of the current ACS signals about the cooling water temperature drop in the crystallizer and its flow rate. It is noted that this system, unfortunately, does not guarantee the detection of local unevenness of the heat removal in the crystallizer and needs to be improved by providing the possibility of assessing the billet faces cooling uniformity. Modern approaches to optimize internal profile of crystallizer sleeves, choice of materials for coating inner surface of sleeves, choice of parameters of mold swinging system and diagnostics of parameters of force interaction between crust of forming billet and mold sleeve are briefly considered on issue of friction rational level establishing. The creation of a “universal” crystallizer with an increased number of control systems and the creation of a system for optimization of casting processes for specific conditions are identified as possible directions for the development of approaches to ensure rational conditions for the formation of continuous cast billets in the crystallizer of a billet caster.

Cold thermopeaking-induced drift of nase Chondrostoma nasus larvae

Research on how intermittent water releases from hydropower plants affect the early life stages of fish has advanced in the last years, focusing not only on the direct impacts of rapid flow changes (hydropeaking), but also on the short-term fluctuations in water temperature (thermopeaking). Flow and thermal fluctuations caused by hydropeaking may affect fish movement patterns and migration at critical stages of a species’ life cycle, e.g., by inducing passive downstream drift. Using two experimental outdoor channels, we investigated how nase (Chondrostoma nasus, Cypriniformes) larvae respond to a rapid drop in water temperature during hydropeaking (simulating a cold thermopeaking event), reaching on average 5.5 °C under peak flow (maximum discharge) conditions, in comparison with a hydropeaking treatment with a constant water temperature regime. Responses of fish larvae were analyzed during acclimation, up-ramping (increase in discharge), peak flow and down-ramping (decrease in discharge) phases. Fish drift increased during peak flow in the cold thermopeaking treatment compared to hydropeaking. Higher drift rates were also negatively associated with pronounced water temperature drops during peak flow conditions. In addition, the starting temperature of the experiment influenced drift during up-ramping. Overall, the results suggest that cold thermopeaking may increase drift in the early life stages of cypriniform fish compared with hydropeaking with stable water temperature. Hence, monitoring and active water temperature adjustments following hydropower releases should be adopted as strategies to mitigate power plant-related impacts on aquatic organisms.

Performance evaluation and model of spacesuit cooling by hydrophobic hollow fiber-membrane based water evaporation through pores

A comprehensive mathematical model is presented that accurately estimates and predicts failure modes through the computations of heat rejection, temperature drop and lumen side pressure drop of the hollow fiber (HF) membrane-based NASA Spacesuit Water Membrane Evaporator (SWME). The model is based on mass and energy balances in terms of the physical properties of water and membrane transport properties. The mass flux of water vapor through the pores is calculated based on Knudsen diffusion with a membrane structure parameter that accounts for effective mean pore diameter, porosity, thickness, and tortuosity. Lumen-side convective heat transfer coefficients are calculated from laminar flow boundary layer theory using the Nusselt correlation. Lumen side pressure drop is estimated using the Hagen-Poiseuille equation. The coupled ordinary differential equations for mass flow rate, water temperature and lumen side pressure are solved simultaneously with the equations for mass flux and convective heat transfer to determine overall heat rejection, water temperature and lumen side pressure drop. A sensitivity analysis is performed to quantify the effect of input variability on SWME response and identify critical failure modes. The analysis includes the potential effect of organic and/or inorganic contaminants and foulants, partial pore entry due to hydrophilization, and other unexpected operational failures such as bursting or fiber damage. The model can be applied to other hollow fiber membrane-based applications such as low temperature separation and concentration of valuable biomolecules from solution.

Hydrogeochemical characteristics and genesis of Hongshuilantang Hot Spring and its water temperature anomalies during the Rushan earthquake swarm in Eastern China

Water temperatures of hot springs close to tectonic fault zones often show some variations before earthquakes, and analyses of earthquake precursors in hot springs have significant referential meaning for earthquake monitoring and forecasting. This study measured the concentration of major ions in water from the Hongshuilantang Hot Spring in 2017 and 2020. The ion composition was classified by hydrochemistry into the HCO3·SO4-Na chemical type. The composition of hydrogen and oxygen isotopes in the Hongshuilantang Hot Spring were located near the global meteoric water line (GMWL), indicating that the recharge source of the hot spring was meteoric water. The δD and δ18O values were not plotted on the Glogal Meteroric Water Line (GMWL), and there were some deviations, which suggested that hot spring water underwent water–rock interactions. Deep circulation water played an important role during the evolution process of thermal water. Water temperature showed a decreasing trend from October 2013 to June 2015 during the Rushan earthquake swarm in eastern China. Because of the occurrence of the earthquake swarm, we inferred that regional stress in this area began to be released, allowing continuous rebalancing. Free surface water appeared in some aquifers, and the seepage of low-temperature underground water into the upper aquifer led to a drop in water temperature in the hot spring. The Hongshuilantang Hot Spring and the epicenter of the Rushan earthquake swarm were located on the Muping–Jimo seismological fault zone, with the same seismotectonic system and some genesis relationships.

Effect mechanism of wind shields on the thermal performance for mechanical draft wet cooling towers

Environmental crosswind is demonstrated to be disadvantageous for the thermal characteristics of mechanical draft cooling towers. To mitigate the adverse effect of crosswind, this study proposes an innovative structural retrofit by adding wind shields with simple structure for both single and double air inlet cooling towers. Numerical investigations are conducted to clarify the effect mechanism of wind shields on tower thermal performance under different crosswinds, through assessing the ventilation rate, the water temperature drop, the air flow field and water temperature field, etc. Results demonstrate that wind shields can eliminate transverse vortices to improve the distribution homogeneity of airflow velocity and water temperature, of which the effects are greatly affected by crosswind velocity and angle. Based on this mechanism, the thermal performance of these cooling towers is prominently strengthened by wind shields when crosswind angle exceeds 45°. The positive effect of wind shields is the most noticeable under a crosswind angle of 90° and a crosswind velocity of 10 m/s, which recovers 17.2 % and 9.4 % of the water temperature drop, and 33.1 % and 19.5 % of the ventilation rate, respectively for the single and double air inlet cooling tower. Present findings can promote applications of wind shields in practical engineering.

Thermal Performance Analysis of Solar Seawater Desalination System Based on Heat Pump Cycle

Mathematical model of the solar seawater desalination system based on heat pump cycle was established, which was solved by programming with MATLAB language. The system performance was analyzed by changing four variables, including the initial temperature of water tank, drive hot water temperature drop, the mass concentration of LiBr dilute solution and the system startup temperature. The results show that increasing the initial temperature of water tank is conducive to reducing the heat consumption of the auxiliary heat source and increasing the solar energy supply ratio; Increasing drive hot water temperature drop is beneficial to increase the fresh water production, but the heat of the auxiliary heat source required increases, and the solar energy supply ratio decreases; Increasing the mass concentration of LiBr dilute solution will not change the total heat consumption of the system, the heat consumption of auxiliary heat sources and the solar energy supply ratio, but the fresh water production will decrease; Increasing the system startup temperature will increase the heat consumption of the auxiliary heat source, reduce the solar energy supply ratio, and slightly reduce the fresh water production.

Experimental study on a multi-evaporator mutual defrosting system for air source heat pumps

Air source heat pumps (ASHPs) are prone to frost when heating in a low-temperature and high-humidity environment, which deteriorates the heating performance of the unit. In this study, a new multi-evaporator mutual defrosting (MEMD) system was proposed to overcome the disadvantages of traditional defrosting methods: intermittent heating and inefficient defrosting. To validate the performance of the proposed defrosting technology, comparative tests were conducted in various outdoor environmental conditions. The experimental results showed that the MEMD system could continuously heat water during the defrosting period. In five experimental conditions, the MEMD system exhibited a lower water temperature drop range (2.1–2.8 °C) than that of a traditional reverse-cycle defrosting (RCD) system (6.0–7.3 °C). Due to the effective utilization of heat production during the heating period, the effective heat power (qe) of the unit increased by 0.7–1.4 kW, and the heat loss coefficient (HLC) of frosting and defrosting increased by an average of 6 % in the five experimental conditions, effectively reducing the heating capacity loss of the unit caused by defrosting. While defrosting, the MEMD system was able to utilize the remaining evaporators to absorb heat from the air and then deliver it to the defrosting evaporator. The equivalent defrosting energy efficiency (COPd) of the MEMD system was 17.5 % greater than that of the RCD system on average. During the heating and defrosting cycle, the energy saved when defrosting could increase the cycle coefficient of performance (CCOP) of heating by 3.7 %.

An optimal operational scheduling model for energy-efficient building with dynamic heat loss prediction

Building energy systems with circulation loops have high circulation heat loss, resulting in low energy utilization efficiency. It requires energy-saving operation strategies to eliminate unnecessary circulation heat loss, especially in domestic hot water (DHW) systems. The objective of this paper is to improve the energy efficiency of building energy systems and reduce operational costs. This is done by dynamically adjusting the target temperature set point. This is the first study to present a computationally inexpensive method for accurately predicting the temperature drop of hot water in environments with changing ambient temperatures. The outcome indicates that energy usage efficiency could be increased by approximately 16.42 %, while operational costs could be lowered by approximately 24.76 % for over 90 days in the fall. The proposed model is an implementable approach for predicting temperature drop and optimal operational scheduling as part of robust and reliable building energy management in real-world scenarios.