COP Values Research Articles

INFLUENCE OF AMBIENT TEMPERATURE ON THE CONTROL OF BODY POSTURE STABILITY IN PROFESSIONAL FIREFIGHTERS

Introduction. Stability of body posture is essential for ensuring safety and achieving highphysical performance. Firefighting, as a high-risk occupation, exposes professionals to factorsthat destabilize balance and posture, increasing the risk of falls and injuries. Extreme thermalenvironments are known to affect postural stability, which relies on dynamic neuromuscularcontrol influenced by vision, body temperature, and psychophysiological state.Objective. This study aims to assess the influence of ambient temperature on the control of bodyposture stability among professional firefighters. Specifically, it examines the role of visual controlin balance maintenance and explores coordination between the nervous and musculoskeletalsystems using posturographic measurements from a force plate (AccuGait). Additionally, thestudy investigates the relationships between posturographic parameters, heart rate (HR), heartrate variability (HRV) and body temperature. The impact of extreme thermal conditions –temperatures exceeding 35C and falling below 0C – on balance maintenance, dizziness, andbalance disorders is also analysed.Material and Methods. Seventeen healthy male volunteers (mean age 35.9 6.1 years, mean workexperience 10.7 5.5 years) were involved in the study. In the first phase, participants completeda survey containing general and detailed questions. They responded with “YES” or “NO” regardingtheir exposure to high temperatures (above 35C) and low temperatures (below 0C). In the secondphase, measurements were taken using the AccuGait force plate (AMTI, USA). Each participantperformed two 30-second trials. The first trial involved standing still on the force plate with openeyes (OE) and closed eyes (CE). Heart rate (HR) and heart rate variability (HRV) were monitoredusing a Polar H7 heart rate monitor and the EliteHRV application. Additionally, infrared photos ofall participants were taken using a FLIR C3X Compact thermal camera.Results. The study revealed that 89.7% of respondents reported experiencing dizziness duringexposure to high temperatures. Force plate testing confirmed excellent postural stability amongfirefighters in both open-eye (OE) and closed-eye (CE) trials. In the CE trial, an 18.9% increase in the average COP velocity (Avg Velocity) and a 19.3% increase in COP path length (Length)were observed. The average heart rate (HR) for the 17 participants was 79.9 15 beats per minute.A correlation was identified between HR and the average COP velocity, COP path length, andthe minimal COP deviation along the Y-axis (AP). The average heart rate variability (HRV) was56.4 8.8 ms, and HRV correlated with the maximum COP value on the Y-axis (AP) during theCE trial. The average corneal temperature was 34.4 1.5C. Statistical analysis was conductedusing Spearman’s rank correlation and the Wilcoxon signed-rank test.Conclusions. The risk of balance disturbances is higher when firefighters operate in hightemperatureenvironments (above 35C) as compared to low temperatures (below 0C). Theabsence of visual control does not compromise the stability of firefighters’ posture, reflecting theirexceptional neuromuscular coordination. The dynamics of muscle force activation in maintainingbody balance are influenced by visual control status and heart rate.

Enhancing Undergraduate Engineering Education: Collaborative and Reflective Practices in Professional Learning Programs for Instructors and GTAs

This study focuses on a professional learning program designed to enhance pedagogical practices for engineering educators at a Canadian university. Rooted in situated learning theory, the program encompasses key themes such as the philosophy of teaching and learning, fostering learning opportunities, designing course for learning, and the scholarship of teaching and learning. Throughout the program, participants, including professors and graduate teaching assistants (GTAs), engaged in understanding student-centered pedagogies, reflective practices, and collaborative learning within Communities of Practice (CoPs). Employing a case study approach, we investigate participants’ learning experiences with the program. The outcomes of this study reveal participants’ emphasis on student-centered pedagogies, recognition of the value of CoPs and instructional coaches, reflection on pedagogical change, and the challenges and tensions encountered during program engagement.

Relevance of Preoperative Cognitive Impairment for Predicting Postoperative Delirium in Surgical Medicine: A Prospective Cohort Study.

Post-operative delirium is a dreaded complication after surgery in older patients. The identification of risk factors for delirium and comprehensive geriatric assessment is an extensive part of recent research. However, the preoperative assessment of risk factors, such as impaired cognition, is frequently not standardized. A comprehensive preoperative assessment was performed in 421 surgical patients to investigate the impact of preoperative cognitive impairment (PCI) on the risk of delirium and to evaluate appropriate screening tools (Six-item screener (SIS) and clock-drawing test (CDT)). Both screening tools showed a significantly increased risk of delirium with p < 0.001 (OR 12.5, 95% [6.42; 24.4]) in SIS and p = 0.042 (OR 2.02, 95%CI [1.02; 4.03]) in CDT for existing cognitive impairment. A higher level of care (p < 0.001) and statutory care (p < 0.001, OR 5.42, 95%CI [2.34; 12.6]) also proved to be significant risk factors. The ROC curves of the two tests show AUC values of 0.741 (SIS) and 0.630 (CDT). The COP values for the SIS are 4 points with a Youden index of 0.447; for the CDT, the COP is 2 (Youden index = 0.177). The recording of PCI should be a central component of the preoperative geriatric assessment. The tools used are simple yet effective and can be easily implemented in routine clinical practice. By reliably identifying patients at risk, the available resources can be personalized and used in a targeted approach.

COOLING PERFORMANCE POTENTIAL OF TEC1-12710 AND TEC1-12715 SR THERMOELECTRIC MODULES WITH HOT SIDE COOLING OPTIMIZATION METHODS USING SEVERAL TYPES OF HEAT EXCHANGERS

Thermoelectric module is a mature technology that have been used in cooling applications such as special product storage cabins and cooling electronic products. Compared to the conventional technology (vapor compression systems), thermoelectric modules offer many advantages. However, in terms of cooling performance, particularly for large cooling capacities (&gt;100Watt), thermoelectric modules still lag the conventional technology. One method that can be used to improve the cooling performance of thermoelectric modules is cooling the hot side of the module using a heat exchanger. In this study, experiments will be carried out on the TEC1-12710 and TEC1-12715 SR modules which alternately combined with five types of heat exchangers on the hot side of the module, connected by thermal paste. The types of heat exchangers used are Square HE, Round HE, Two-Pipe HE, Four-Pipe HE, and Liquid-Cooler HE. The experiments are carried out with operating voltage variations of 12V, 9V and 6V for each thermoelectric module. The data analysis results found that the best COP value was obtained by the TEC1-12715 SR thermoelectric module with the Round type Heat Exchanger of 0.767 at a voltage of 6V. For the TEC1-12710 thermoelectric module, the highest COP value was also obtained when the module was paired with a Round type Heat Exchanger at a voltage of 6V, with a value of 0.620. Additionally, the highest heat absorption value for both thermoelectric modules was obtained at a voltage of 12V using the Round type heat exchanger, namely 19.61 Watts (TEC1-12710) and 26.98 Watts (TEC1-12715 SR), respectively.

The thermodynamic and environmental analysis of a variable speed R404A refrigeration system using R455A

The suitability of drop-in application of low-GWP refrigerant R455A in a R404A refrigeration system is experimentally investigated in this paper comparing energy performance and environmental impacts (i.e., CO2 emissions) of the system. The evaporation temperatures are −5, 0 and + 5 °C while condensation temperatures are 30, 40 and 50 °C in the test conditions. Besides, the compressor speed is adjusted for three cases as 40, 45 and 50 Hz. The behaviours of COP, exergy efficiency and total equivalent warming impact (TEWI) are determined depending on evaporation and condensation temperatures as well as compressor speed. The results demonstrate that although cooling capacity of R404A is higher, COP of R455A is computed to be better than R404A about by 4.3 % (on average) for all covered cases. The exergy efficiency of R455A is also found to be higher compared to R404A. The COP and exergy efficiency values are reduced, TEWI enhances as compressor speed increases for both R404A and R455A. Additionally, an empirical expression (valid within about ± 5 % and independent of variable parameters such as refrigerant type, compressor speed as well as evaporation and condensation temperatures) is proposed for the relationship between nondimensional parameters COP and compression ratio. Furthermore, the amount of TEWI is verified to be lower for R455A than R404A, hence the studied alternative blend can be preferred due to the environmentally friendly characteristic. It can be suggested referring to the obtained results that R455A can be directly used in a R404A refrigeration system due to improved thermodynamic performance and diminished CO2 emissions.

Experimental Assessment of a Refrigeration System Powered by a Gasoline Engine Utilizing GasolineBioethanol Mixture

Dependable refrigeration is essential for vaccine preservation, especially in distant and resourcelimited areas with unstable electrical supply. Gasoline-powered refrigeration systems present a viable option to electric-powered units; however, their efficacy and environmental consequences necessitate comprehensive assessment. This study investigated the experimental evaluation of a gasoline-powered refrigeration system featuring a micro-cooling compartment specifically intended for vaccine storage. Gasoline-bioethanol blends (E0, E5, E10, and E15) were evaluated in a fourstroke spark-ignition engine to enhance fuel economy and environmental sustainability. The physicochemical characteristics of these blends, such as pour point, octane number, cetane number, viscosity, density, carbon residue, and heating values, were examined to ascertain the optimal fuel composition. The system's effectiveness was estimated using COP. The findings reveal that the E10 gasolinebioethanol blend exhibited significant performance attributes, featuring appropriate octane ratings, viscosity, and density, alongside less carbon residue of 74% and an improved heating value of 410 MJ/kg and COP value of 12%. The employment of the E10 blend significantly reduced CO₂ emissions and enhanced engine performance, rendering it a viable fuel option for gasolinepowered refrigeration systems in this context. This study emphasizes the promise of E10 as a more environmentally friendly and efficient fuel option for gasoline-powered refrigeration systems, enhancing engine performance and aiding in the reduction of carbon emissions. This research provides significant insights into sustainable refrigeration options for vaccine preservation in environments where conventional refrigeration is impractical, hence enhancing public health in neglected communities.

Model-based improvement of a trans-critical CO2 refrigeration plant

Abstract Refrigeration sector including heat pumps, cryogenics and air conditioning is responsible for a share close 10% of the global greenhouse gas emissions. Therefore, a huge effort of the scientific and industrial community is needed on the development of technologies allowing to reduce the environmental impact of this sector. The use of CO2 as working fluid has great interest in food chain conservation and participates to the problem of the impact produced by the traditional synthetic fluids, recently oriented also to hydrocarbons. Main problem of plants using CO2 as working fluid is the low COP, which reduces even more in moderate or hot climate regions in which low temperature thermal energy is more required. To assess the benefits introduced by plant optimization and innovative technologies, many advanced thermodynamic models are developed in the last years. Anyway, few software platforms are developed for the comprehensive analysis of plant behaviour. To fill this gap, this paper presents the results of a theoretical and experimental research done on an industrial trans-critical CO2 refrigeration plant. The aim was to set up energy saving solutions finalized to mitigate the intrinsic low COP values. A detailed physically consistent model of the unit has been developed following an integrated zero and mono-dimensional thermo-fluid-dynamic approach. The propagative, capacitive, and inertial properties of the components have been considered, so going beyond of the theoretical approaches that are typical in the sector. A wide experimental characterization of the unit has been done with the aim to validate the model and to use it as tool to predict the effect on the COP of the operating variables. The reduction of the compressor absorption and the potentiality of the energy recovery from energy usually wasted have been analysed.

Targeted medical treatment of patients with chronic thromboembolic pulmonary hypertension who undergo balloon pulmonary angioplasty

Abstract Introduction In patients with chronic thromboembolic pulmonary hypertension (CTEPH) who undergo balloon pulmonary angioplasty (BPA), pre-treatment with PH-targeted medical therapy may be beneficial in improving clinical parameters and pulmonary hemodynamics. Purpose This study aims to describe the clinical results of PH-specific therapy prior to BPA. Methods Patients with CTEPH who underwent BPA treatment were selected from the St. Antonius CTEPH database. Medical treatment strategy, clinical parameters, and pulmonary hemodynamics at time of diagnosis and at the first BPA were collected from medical records. Results In total 93 BPA patients (62.4% women; age 60.4±14.1 years; NYHA FC III/IV 60.9%) were included; the majority of patients received dual PH targeted medical therapy (64.1%). Between diagnosis and the first BPA significant improvements were observed for both clinical parameters (6MWD: 26.8m [5.2 - 48.4], Log NTproBNP: -0.5 pg/ml [-0.8 to -0.2]) and pulmonary hemodynamic (mRAP: -2.2 mmHg [-3.7 to -0.8], mPAP: -6.4mmHg [-8.3 to -4.5], CO: 0.5L/min [0.2 - 0.9] and PVR: -2.6WU [-3.3 to -2]). Dual PH targeted medical therapy resulted in significantly greater improvements in PVR (p = 0.03) in comparison to patients without and mono PH targeted medical therapy (CO and mPAP both p-value: 0.01). Conclusion Between diagnosis and the initial BPA, substantial improvements were observed for 6MWD, NTproBNP and most pulmonary hemodynamics in CTEPH patients who underwent BPA. Patients who received dual PH targeted medical therapy had significantly greater improvements compared to patients without (PVR) and on mono PH targeted medical therapy (CO and mPAP).Clinical parameters: Baseline-1st BPAPH medication: ANOVA Post hoc analyses

Experimental study and simulation of a solid desiccant cooling system installed in northern Algeria

An experimental investigation of a solid desiccant cooling system for a research laboratory on the Algerian coast has been carried out. The system utilized flat-plate solar collectors for regeneration and was evaluated through a combination of individual component characterization, system modeling (using TRNSYS), and experimental validation. The results obtained have been validated and show that the efficiency of the rotary heat exchanger reached 65 %, the evaporative humidifier efficiency reached 94 %, and the desiccant wheel achieved efficiencies of 73 % on the process side and 66 % on the regeneration side. This translates to a significant dehumidification effect, reducing absolute humidity in the treated air by 9 g/kg, for the supply air temperature effectively maintained at a comfortable 24 °C. The close agreement between the simulated and experimental COP values (1.13 and 1.08, respectively) validates the chosen approach and confirms the potential of this technology for energy-efficient building cooling in the hot and humid Mediterranean climate of northern Algeria.

Testing the Efficiency of a Heat Pump with Radiant Systems in Heating Mode

The paper deals with the experimental testing of the efficiency of the operation of an air/water heat pump in connection with three radiant systems in heating mode in an office building, which is part of the central laboratories of the Slovak university of Technology in Bratislava. The testing was aimed at verifying the manufacturer's theoretical claims about efficiency of the heat pump based on the COP and SCOP values according to EN 14511-1:2022 and EN 14825:2022. The testing period was from 7 Jan. 2024 until 15 Jan. 2024. The aim of the testing measurements was to evaluate the calculated value of SPF efficiency for individual days and for the testing period. During the measuring period, the wall radiant system consumed 188 kWh, the ceiling system 216 kWh, and the floor radiant system 196 kWh. The heat pump consumed 227 kWh of electricity. The calculated SPF value was 2.64.

Design and experimental characterization of a propane-based reversible dual source/sink heat pump

The current paper presents the design and energy performance analysis of a propane-based reversible Dual Source/Sink Heat Pump (DSHP). DSHPs offer an alternative to conventional water to water and air to water heat pumps, leveraging the strengths of both technologies in an efficient manner. The developed prototype incorporates an innovative Dual Source/Sink Heat eXchanger (DSHX), enabling the unit operating in various modes, including space heating, space cooling, and domestic hot water production using brine, air or both simultaneously as a source/sink. The DSHX serves as as both a condenser or an evaporator, directly rejecting or absorbing heat from air and/or brine. By eliminating secondary loops and defrost cycles, the DSHX minimizes energy losses. The main novelty of this work lies in the DSHX that integrates external units typically duplicated in DSHPs into a single component, eliminating the need for split refrigerant flow rates, thus avoiding maldistribution, refrigerant charge increase and draining valves. A steady state experimental campaign was conducted in a climatic chamber to characterize the DSHP prototype and validate the DSHX performance models. Heating capacity up to 11.2 kW and COP values up to 4.7 were achieved at nominal compressor speed by supplying hot water at 35 °C with an ambient temperature of 7 °C. Similarly, when producing cold water at 7 °C, cooling capacity and EER reached 9.8 kW and 3.6, respectively, at nominal compressor speed using air as heat sink at 35 °C. The effects of various operating parameters on the overall coefficient of performance and heat duty in both heating and cooling modes, considering air or brine as heat source/sink are analyzed in detail. Results demonstrate enhancements of approximately 15 % in capacity and efficiency compared to earlier work. Moreover, four deterministic models were created in order to predict the behaviour of the DSHX and validated against experimental results, reaching deviation values below 15 %.

A statistical physics-based methodology for evaluating the efficiency of an adsorption refrigeration cycle using C3H2F4/Maxsorb III

Recently, the statistical physics modeling found a great success in the description of various aspects of adsorption phenomena such as olfaction, depollution, and photovoltaic processes. Therefore, we attempted here to apply this treatment in the domain of refrigeration by an adsorption/ desorption process cycle, using the grand canonical formalism of the statistical physics as a working tool. So, for this study, four advanced equations based on statistical physics treatment are used to clarify the adsorption process at molecular level and define its physico-chemical parameters for refrigeration applications. Our results showed that the double layer model with two energies provides useful details concerning this phenomenon by determining the number of captured HFO-1234ze (E) (C3H2F4) molecules per site nAM, the density of receptor site Drs, the adsorption quantity at saturation N a sat and two energetic parameters Phs1 and Phs2. The steric results revealed that the adsorbed C3H2F4 molecules tended towards a parallel position when the temperature increased. Evaluations of the adsorption energies and enthalpy values indicated that the anchoring process is exothermic and of a physisorption nature. In order to improve the thermodynamic efficiency, the coefficient of performance was calculated by analyzing changes in thermodynamic functions, giving a value of 0.58 for the C3H2F4 / Maxsorb III. Also, the COP value can be enhanced by using the same adsorbate with high compressibility to minimize the machine size but changing the present adsorbent by activated carbon derived from biomass such as: Waste Palm Trunk (WPT-AC) and Mangrove wood (M−AC).

Preliminary study of the thermoelectric cooler and heat pipe application for the cooling system in cabin pickup car

Abstract Car cooling systems are essential equipment to make passengers comfortable, but their energy consumption is very high. Thermoelectric technology has been widely applied as a cooler in many applications, but its use as a car cooler has not been widely used. This research aims to conduct a preliminary study using thermoelectric coolers (TEC) as alternative coolers in pickup cars and to investigate the effect of thermoelectric module and heat exchanger configurations on cooling systems performance. A-TEC cooling system usually uses conventional heat sinks on the cold side and hot side of the TEC. In this study, heat pipes are used as heat exchangers on the hot side of TEC to improve its performance. The cooling system consists of 2 units installed at the rear of the pickup car cabin. Tests were varied using 2 TEC modules arranged in series and 4 TECs arranged in parallel thermal and electrical series. The results showed that using two cooling system units consisting of four TEC modules equipped with heat pipes was able to cool the temperature of the pickup car cabin at 27.4 °C and obtained the highest COP value of 1.16. It shows heat pipes can enhance TEC cooling system performance, producing lower cabin temperatures than conventional heat sinks.

Energy, exergy, environmental, and economic (4E) analyses of the usability of various nano-sized particles added lubricant in a heat pump system

The need for energy is rising significantly with the growth of technology in the world. This energy need is largely met by fossil fuels. The enhancement in their prices and the damage they induce to the environment, scientists have turned to alternative energy sources due to the depletion of fossil fuels. In recent years, these alternative energy sources have come to the fore as solar, wind, and wave energy. However, heating and refrigeration systems, whose share of energy consumption in buildings in the world is 40 %, can also compete with these alternative energy sources. In particular, heat pumps (HP) are at a level that can compete with renewable energy sources to seriously reduce this rate. In this study, different nanoparticles were added to the Polyol ester oil (POE) utilized in the compressor to enhance the performance of the HP. Thermodynamic, environmental, and economic performances of the obtained nanolubricants at different concentrations (0.5 wt% and 1 wt%) and flow rates (15, 30, and 45 g/s) were evaluated. The highest COP value of the HP was calculated as 4.14 at 0.5 wt% B-POE at 45 g/s. The best energy consumption in the HP was obtained with 0.5 wt% B-POE nanolubricant with a decrease of 10.96 % at 45 g/s compared to pure POE. The highest exergy efficiency in the HP was calculated at 0.5 wt% B-POE nanolubricant with a 13.53 % increase at 30 g/s compared to pure POE. The best exergoeconomic parameter (Rg,ex) performance was determined as 3.7148 kWh/$ in 1 wt% TiO2-POE nanolubricant at 45 g/s. The best enviro-economic value of 0.16182 ¢/h was obtained with 0.5 wt% B-POE nanolubricant at 45 g/s. In line with the results obtained, it was observed that the B-POE nanolubricant has a performance that can compete with the good-performing TiO2-POE nanolubricant.

A Novel solar-assisted air source heat pump system for urban renewal: Experimental test and numerical simulation

Old residential communities require novel heating solutions to meet heating demands sustainably. In Southern China, current heating systems in old communities have high energy costs and lack sustainability. A potential solution, air source heat pumps (ASHP), have evaporators susceptible to frost accumulation and poor heating performance at low ambient temperatures. This study proposes a hybrid design that uses additional solar thermal energy to improve energy gains from the air source; the innovative serial coupling design increases the air-source temperature by engineering the evaporator of the ASHP as the load-side of the heat exchanger. The novel hybrid design aims to be efficient, cost-effective, and sustainable, satisfying urban redevelopment needs. A prototype of the novel hybrid solar-assisted ASHP system was constructed; various performance parameters were evaluated, and system operation in extreme climates was simulated in TRNSYS. Results indicated that the novel hybrid system had significantly superior heating performance, delivering a 70.1% improvement in heating rate compared to single-source ASHP under lower ambient temperatures (13C). The novel hybrid system also had a high COP value between 5.7 and 6.3, significantly exceeding values of 2.3-3.5 for most air-conditioning units. It demonstrates consistent performance in all simulated climates. It is estimated that the novel hybrid system can save 1000 RMB in annual energy costs for an average Shanghai family and reduce Shanghais CO2 emissions by 4.7 million tons. The novel system addressed limitations of ASHP, optimizing performance while maintaining sustainability, offering a promising solution for urban renewal projects in China.

Energy, exergy, environment and economic (4E) analysis of PV/T module assisted vapor compression refrigeration system: An experimental study

Despite the rise in the prices of fossil fuels, the increase in their demand, and damaging the environment, a large part of the world's energy needs have been today met by fossil fuels. In this direction, interest in renewable energy sources has increased. Solar energy stands out among renewable energy sources because it is endless and clean. However, today, the use of solar energy is not used alone, but in combination with other thermal energy systems. In building applications, it is mostly used in heating, refrigeration, and HVAC systems, which have a high part in energy consumption. In this study, the solar energy and cooling system were not used separately as in previous studies but were used as a hybrid. The focus was on increasing the performance of both systems by operating them together. In this study, energy, exergy, thermoeconomic, and environmental analyses were applied to the PV/T-assisted vapor compression refrigeration system (PV/T-VCRS) at different storage temperatures (25 °C, 30 °C, and 35 °C). As a result, an 8.5 % lower surface temperature of the module in PV/T-VCRS 25 °C was measured compared to PV/T-VCRS 30 °C and 35 °C. In direct proportion to the module surface temperatures, 13 % better electrical efficiency was obtained in PV/T-VCRS 25 °C compared to 30 °C and 35 °C. The COP value increased by 15.46 % in PV/T-VCRS 25 °C compared to 30 °C and 35 °C. A 13 % improvement in exergy efficiency was observed in PV/T-VCRS 25 °C compared to 30 °C and 35 °C. The enviroeconomic parameter PV/T-VCRS is calculated as 15.17 ¢/h, 16.52 ¢/h, and 17.6 ¢/h for 25 °C, 30 °C and 35 °C. Another advantage of the system is that hot water is obtained at set temperatures. In PV/T-VCRS, 475 L, 300 L, and 210 L of hot water were obtained at 25 °C, 30 °C, and 35 °C, respectively. As a result, the performance of the PV/T-VCRS was good, with the added benefit of performing close to the performances when PV/T and VCRS were used separately.

Investigation and thermodynamic analysis of hydrogen liquefaction cycles: Energy and exergy study

The use of hydrogen as a clean fuel has drawn the attention of many scientists due to the problem of energy and environmental pollution caused by fossil fuels. One of the important requirements for expanding the use of hydrogen is the investigation and thermodynamic analysis of liquefaction cycle; this includes the thermodynamic investigation of different cycles of hydrogen liquefaction in pre-cooling and cryogenic cooling. Thermodynamic analysis comprises an examination of the cycle's energy and exergy, as well as the equipment employed. In this research, three liquefaction cycles with different pre-cooling cycle and cryo-cooling cycle have been evaluated. The use of organic Rankine cycle (ORC) and liquefied natural gas (LNG) has also been applied in the cycles and the arrangement of the equipment. Simulations and analyzes have been done in Aspen HYSYS V12. The results show that in the pre-cooling process of cycles 1, 2, and 3, the amount of useful exergy is 49.87 %, 58.87 %, and 61.21 %, respectively, which means that the third cycle uses the input exergy better. Also, in the pre-cooling process of cycles 1, 2, and 3, the amount of exergy loss is 33.86 %, 26.77 %, and 19.73 %, respectively, which means that the third cycle has less exergy loss in the pre-cooling process. The findings indicate that in each of the three cycles, over 50 % of the input exergy is wasted in the cryo-cooling process. Value of specific energy consumption (SEC) for cycle 1,2, and 3 is equal to 6.605 kWh/kgLH2 , 6.601 kWh/kgLH2 and 6.618 kWh/kgLH2, respectively. The three cycles under examination had COP values of 0.19945, 0.19936, and 0.19884, in that order. Also, the values for EXE cycles 1, 2, and 3 are 45.816 %, 45.883 %, and 45.797 %, respectively. Analyzing the energy and exergy of liquefaction cycles is a good step toward increasing cycle efficiency, identifying weak places, and altering cycles to improve efficiency.

Energy and exergy analysis of a novel two-stage ejector refrigeration cycle using binary zeotropic mixtures

To improve the ejector refrigeration cycle performance, this paper presents a theoretical thermodynamic analysis of a novel two-stage ejector refrigeration cycle (TSERC) with a gas-liquid separator using R134a/R32 and R600a/R290 as refrigerant. By separating the relatively low-boiling-point and high-boiling-point refrigerants, the cycle compression ratio decreases, the cycle performance increases, and the energy utilization efficiency can be improved. Energy and exergy analysis were conducted for the traditional single-stage ejector refrigeration cycle (SSERC) and TSERC. The effect of the mixture mass fraction on cycle performance under a fixed external heat source operating condition was studied, and the cycle performance comparisons between TSERC and SSERC at different evaporation temperature, condensation temperature and generation temperature were conducted. Results show that for TSERC, the maximum COP values 0.126 and 0.11, the maximum exergy efficiency 4.51 % and 4 % are obtained as the low-boiling-point mass fraction equals 0.6 and 0.4 respectively for R134a/R32 and R600a/R290. It is found that exergy destruction mainly occurs in the low-pressure sub-cycle of TSERC, the top three largest exergy destruction components are ejector 1, condenser 1 and generator 1, while the smallest exergy destruction occurs in pump 2. In addition, cycle performance comparison between SSERC and TSERC shows that the maximum COP improvement increased by 41.6 % and 89.6 % for 134a/R32 and R600a/R290 for TSERC, while the maximum entrainment ratio improvement increased by 32.4 % and 87.6 %. Moreover, it is concluded that the cycle performance improvement of TSERC is more significant at lower evaporation temperature, higher condensation temperature, and lower generation temperature compared to SSERC.

Advanced vapour compression refrigeration system dispersed with hybrid Nanolubricants: ANN-Based approach

In this study, the R600a refrigerator’s performance evaluation has been investigated utilizing the implementation of hybrid nanolubricants (SiO2/CuO) at various quantities and mass charges. The outcomes of the experiments compared to those achieved using SiO2/CuO hybrid nanolubricants and R600a charges are examined. Hybrid nanolubricants are used as substitutes for pure lubricants, and the performance parameters are assessed against the results of the experiments. SiO2 at 0.2 g/L and CuO at 0.4 g/L hybrid nanolubricants provided an optimal cooling effect of 259 W and consumed a minimum quantity of energy of 73 W resulting in a maximum enhanced predicted COP value of 3.547 compared to experimental results. The clean lubricant system resulted in a minimum COP and refrigeration effect of 2.6 and 246 W and consumed more energy of 95 W. It has been observed that adding hybrid nanoparticles to compressor mineral oil substantially loweredcompressor energy consumption and enhancedrefrigeration effect, refrigerator performance. By using the ANN prediction approach, the use of SiO2/CuO hybrid nanolubricants led to maximum increased COP, refrigeration effect, and lower energy consumption when compared with experimental findings.

Cost-Effective Control of Hybrid Ground Source Heat Pump (GSHP) System Coupled with District Heating

Hybrid ground source heat pump systems (GSHP) offer energy flexibility in operation. For hybrid GSHP systems coupled with district heating, limited studies investigated control strategies for reducing system energy costs from the perspective of building owners. This study proposed a cost-effective control strategy for a hybrid GSHP system integrated with district heating, investigating how power limits of district heating/GSHP, COP value for control (COPctrl), and control time horizon impact the system annual energy cost, CO2 emissions, and long-term borehole heat exchanger system performance. The simulations were performed using the dynamic building simulation tool IDA ICE 4.8. The results indicate that to realize both the energy cost savings and the long-term operation safety, it is essential to limit the heating power of district heating/GSHP and select an appropriate COPctrl. The control time horizon insignificantly affected the annual energy cost and long-term borehole heat exchanger system performance. The recommended COPctrl was 3.6, which is near the GSHP seasonal performance factor. Eventually, the cost-effective control reduced the system’s annual energy cost by 2.2% compared to the GSHP-prioritized control. However, the proposed control increased the CO2 emissions of the hybrid GSHP system due to the higher CO2 emissions from district heating.