Higher Coefficient Of Performance Research Articles

High-accuracy experimental study of performance characteristics of optimised Ranque-Hilsch vortex tube

In this paper we present high-accuracy experimental measurements of the performance characteristics of an optimised Ranque-Hilsch vortex tube of cylindrical counter-flow design. Although this is a relatively mature research area, the published high-accuracy experimental data with quantified measurement uncertainty is very limited. The purpose is to provide a reference data-set for CFD method validation and calibration. The vortex tube design is a performance-optimum based on existing literature. We characterize the temperature separation, energy separation, efficiency, and coefficients of performance for three inlet pressures (3.0 bar, 5.0 bar and 7.0 bar) and for atmospheric back pressure. Performance characteristics are presented as a function of cold gas mass fraction. The lowest non-dimensional cold-exit temperature (normalised by inlet temperature) was 0.87, the highest coefficient of performance (decrease in enthalpy flux of the cold stream normalized by work needed to compress air to the inlet pressure) was 0.137, and the highest isentropic efficiency (ratio of the actual energy lost by cold stream to energy that would have been lost in an isentropic expansion of the entire inlet stream from the inlet pressure to the cold-exit pressure) was 0.16.

Thermodynamic Simulation of Cascade Cooling System for Vacuum Freeze Drying

Vacuum freeze drying (VFD) is a drying method carried out at pressures and temperatures below the triple point of water. Drying occurs by sublimation. The results of the VFD method are able to maintain the quality of dry ingredients (taste, colour, nutrient, etc.). To achieve a condition below the triple point of water, it is conditioned so that the pressure is under a partial pressure of 6.11657 mbar at a temperature of 0.01°C. The refrigeration system is simulated using refrigerants R-134a and R-22. The purpose of the simulation is to obtain the optimum system conditions. The variables varied were the saturated temperature of the LTC (Low-Temperature Circuit) evaporator, the saturation temperature of the HTC (High-Temperature Circuit) evaporator, the difference in the temperature of the pinch point between the LTC condenser and the HTC evaporator and the temperature of the HTC condenser. The simulation results are the saturated temperature of the LTC evaporator -30°C, the saturation temperature of the HTC evaporator -15°C, the difference in the temperature of the pinch point between the LTC condenser and the HTC evaporator 10°C and the temperature of the HTC condenser 40°C. The highest Coefficient of Performance (COP) of the cascade cooling system with these parameters is 2.55 using a combination refrigerant R22 in HTC and R134a in LTC.

R290 Refrigerant Performance in a Commercial Refrigerator

In this study, we investigated the impact of the environmentally friendly R290 refrigerant, which has a higher Coefficient of Performance (COP), on the operating performance of the cooling system, as an alternative to the commonly used R404A refrigerant, which has a negative effect on global warming. The boundary conditions in the refrigeration cycle were designed to be -10°C evaporation and +45°C condensation, and the performance of the system referenced in the TS EN ISO 23953-2 standard was experimentally compared for both refrigerants. The temperature and energy consumption values of the M-packs, whose location and quantity are specified in the relevant standard, have been evaluated in terms of the cooling performance of the cabinet. As a result of the study, the heat removal performance of the system using R290 fluid in the condenser showed better results compared to R404A. According to the relevant standard, the system using R290 is in the C and D classes in the energy consumption evaluation.

Centrifugal compressor design and cycle analysis of large-scale high temperature heat pumps using hydrocarbons

Using natural refrigerants in heat pumps, including hydrocarbons, is becoming attractive because of the tightening regulations concerning synthetic refrigerants. In the literature there is lack of studies investigating detailed component design, including compressor design when using hydrocarbons. This study investigates numerically centrifugal compressor design with hydrocarbons for large-scale high-temperature heat pumps. The compressor analysis was combined with a thermodynamic analysis of a two-stage heat pump. The effect of temperature lift and flash intercooler temperature on compressor sizing, rotational speed, efficiency, axial force, and Mach number were investigated. Generally, the use of hydrocarbons with five carbon atoms resulted in higher coefficient of performance and required lower compressor rotational speeds and larger compressor dimensions when compared to the hydrocarbons with four carbon atoms. The simulated rotational speeds were ranging from 8 krpm to 30 krpm, impeller diameters from 0.15 m to over 0.7 m and compressor efficiencies from 77% to over 85%. The use of cyclic molecules, namely cyclopentane and cyclobutene resulted in the highest heat pump coefficient of performance. Also, the flash intercooler temperature had a notable effect on the compressor design and axial force which has to be taken into account in heat pump cycle design.

Performance analysis of a two-stage evaporation heat pump drying system for graded cooling/dehumidification

Single-stage evaporation heat pumps are widely used in drying fields, but they suffer from relatively low efficiency. To enhance the performance of conventional heat pump drying systems with single-stage evaporating, a two-stage evaporation heat pump drying (TSE-HPD) system is proposed in this paper for graded cooling/dehumidification. In this innovative system, the quasi dual-stage compression, matching a double temperature level evaporation process, achieves graded cooling and dehumidification of air. Its performance is investigated using energy and exergy analysis methods and compared with that of a single-stage compression heat pump drying (SSC-PHD) system. The results indicate that the TSE-HPD system exhibits 15.5 %–19.3 % improvement in the coefficient of performance (COP) and 16.3 %–18.9 % enhancement in the specific moisture extraction rate (SMER) compared to those of the SSC-PHD system when the condensing temperature varies between 50 °C and 70 °C. The parametric analysis reveals that the highest COP, SMER, and exergy efficiency (ηex) occur when the optimum first-stage evaporating temperatures are 16 °C, 25 °C, and 34 °C, respectively, under three standard operating conditions. At this time, the first-stage evaporator handles 36 %–40 % of the cooling/dehumidification tasks, the refrigerant mass flow ratio at the intermediate-pressure suction port of the compressor ranges from 47 %–58 %, and the optimum first-stage and second-stage compression ratios are 1.49–1.52 and 2.45–2.61, respectively. The research results provide guidance and reference for the determination of matching design parameters and efficient operation control parameters of drying systems.

A dynamic simulation study of temperature and humidity independent control system for temperate semi-humid continental monsoon climate regions

A temperature and humidity independent control (THIC) system is a promising solution for hot and humid indoor working environments. This study proposes a dual-source heat pump air-conditioning (DSHPAC) system composed of a dual-source heat pump (DSHP) and air handling unit (AHU) as a THIC system. The proposed THIC system indirectly adjusts the cooling capacity of the high-temperature evaporator (Eva1) and low-temperature evaporator (Eva2) by controlling the refrigerant mass flow rate of the system to meet the cooling and dehumidifying requirements under different operational conditions. The proposed THIC system can switch among three operational modes by using the designed operational strategy, ensuring that the requirements for indoor temperature and humidity are met. In addition, the mathematical model and equilibrium equations of the THIC system are established. This study uses an office building in Xi'an on a typical summer day as a simulation case in dynamic simulations. The coefficient of performance (COP), cooling capacity, and compressor power consumption of the proposed DSHP system are analyzed. The results demonstrate that the COP of the proposed system increases with the temperature of Eva1 (TEva1), the COP of the proposed system varies from 1.76 to 3.62, and the cooling capacity increases from 1.19 kW to 3.38 kW when TEva1 increases from 6.24 °C to 36.4 °C. The analysis of different values of φR (refrigerant mass ratio) shows that the highest COP is achieved at φR = 0.1. The results prove the application potential of the dual-source heat pumps to the THIC air-conditioning systems.

Computer-aided molecular refrigerant design for adsorption chillers based on classical density functional theory and PC-SAFT

Adsorption chillers are a promising technology for sustainable cooling. The performance of adsorption chillers is highly influenced by the selection of the refrigerant. Still, systematic selection of refrigerants is challenging because evaluating adsorption properties requires significant experimental or simulation efforts. Thus, refrigerant design options are often limited.Here, we propose a systematic refrigerant design method for adsorption chillers assessing refrigerants based on their process performance. Our method quantifies adsorption isotherms by 1-dimensional classical density functional theory (DFT) based on the PC-SAFT equation of state. The method is used to screen over 1800 refrigerants based on their coefficient of performance (COP). We identify refrigerants with higher COPs than commonly used refrigerants and highlight the advantage of a process-based objective function over material-based heuristic selection criteria. Finally, we advance from screening to computer-aided molecular design of the refrigerant, leveraging the efficiency of the DFT model to explore the molecular design space systematically.

The effects of Multiwalled Carbon Nanotube to the performance of a refrigeration system

By incorporating nanofluid technology and nanolubricants into compressors, the performance can be enhanced while also lowering worldwide fuel consumption and aiming at developing cleaner, more efficient energy sources and uses. The globe is being confronted with energy security issues and heating, cooling and HVAC systems highly contribute to it. Hence, it is critical to save energy and improve the efficiency of the refrigeration cycle. This study presents experimental and theoretical findings in order to investigate the effect of Polyester (POE)-oil based multiwalled Carbon Nanotube (MWCNT) nanolubricant on the Coefficient of Performance (COP) of a refrigeration system. The objectives of this study is to analyze the stability of MWCNT nanofluids, to obtain the COP of a refrigeration cycle run with pure POE oil and MWCNT nanofluids with different concentrations respectively. The experiment was conducted by preparing 0.55, 0.65 and 0.70 g/l MWCNT nanofluid by using the two step method. The most effective concentration used in the refrigeration system was referred to the one that resulted in the highest COP. It was determined from the experiment that 0.55 g/l MWCNT nanofluid resulted in a higher COP of 5.766 as compared to the other two concentrations. Besides, it showed an improvement of 34.6% in COP as compared to the COP of using pure POE oil in the refrigeration system, which was found to be 4.285. The 0.65 g/l and 0.70 g/l concentration of MWCNT resulted in a COP of 5.618 and 5.617, respectively. The compressor work was also analyzed and was found to be reduced noticeably after adding MWCNT nanoparticles. Hence it can be concluded that the increment of MWCNT concentration in nanofluids increases the COP of the refrigeration system but only up to a certain limit of concentration.

Operating characteristics and evaluation of air source heat pumps in cold regions during heating season in China

The mismatch between the actual heat production of an air source heat pump (ASHP) and the instantaneous load of the building it heats is a critical cause of low energy efficiency. Research on the measured heating effect provides an effective approach to improve the energy efficiency of an ASHP. This study therefore focused on two small office buildings to explore the operating data describing the ASHP system source and load sides during the heating season. A sensitivity analysis was employed to explore the actual operational effects of the ASHP. Common problems associated with system operation were comprehensively identified, including the operation characteristics, energy efficiency coefficients, load characteristics, and energy consumption characteristics of the transmission and distribution systems. The effects of these problems were evaluated from three perspectives: integrated part load value (IPLV), system performance loss, and indoor environmental parameters. The results shows that the highest coefficient of performance (COP) of the ASHP in Building A was 3.27 while the IPLV was 2.68, operating status reached the standard. The COP value of the ASHP in Building B was 1.55 while the IPLV was 2.45. Poor value shows the low performance in operating phase, which can be further optimised by matching the building instantaneous load to the heat production of the ASHP, improves the operating effect of two buildings comprehensively.

Maximizing efficiency in solar ammonia–water absorption refrigeration cycles: Exergy analysis, concentration impact, and advanced optimization with GBRT machine learning and FHO optimizer

A detailed analysis of energy and exergy is conducted on a single-effect solar ammonia–water (NH3–H2O) absorption refrigeration cycle (ARC) using TRNSYS and EES software. Considering the physical and chemical exergies, the exergy destruction rate (ĖD) in each component of the system is calculated, highlighting its contribution to the overall ĖD. The study explores the effects of varying refrigerant mass flow rate (ṁᵣ) and ammonia concentration in strong and weak solutions (Xs and Xw) on key performance parameters, including coefficient of performance (COP), exergy efficiency (ĖD), and overall ĖD across a range of generator temperatures (Tg). In this study, a gradient boosting regression tree (GBRT) is employed as a supervised machine-learning technique for classification and regression problems, utilizing boosting to enhance conventional decision tree predictions. The Fire Hawk Optimizer (FHO) approach is also utilized to optimize performance parameters, maximizing COP and ηηEwhile minimizing Tg and ĖD. The GBRT models are developed using available experimental and simulation data, revealing relationships between variables (ṁᵣ, Xs, Xw, and Tg) and outcomes (COP, ĖD, and overall ĖD). The results revealed that the generator exhibits considerable ĖD regardless of operating conditions, underscoring its pivotal role in the ARC. It emerges as the primary ĖD contributor (50 %), followed by the evaporator (17 %) and the absorber (15 %). However, ĖD associated with the recooler, pump, and expansion valves is negligible in comparison. Optimization results reveal that, when minimizing Tg and ĖD, the highest COP and ĖD at Tg of 373.15 K reach 0.8081 and 0.46, respectively.

ENERGY, ENVIRONMENTAL, AND EXERGOECONOMIC (3E) ANALYSIS OF TRANSCRITICAL CO2 BOOSTER AND PARALLEL COMPRESSION SUPERMARKET REFRIGERATION CYCLES IN CLIMATE ZONES OF TÜRKİYE

Legal restrictions on high-GWP refrigerants lead to the widespread use of carbon dioxide in commercial refrigeration, where there is a high energy consumption. Although CO2 has many benefits, its lower critical temperature and higher operation pressure compared to other refrigerants lead to performance reduction. For this reason, studies have been conducted by researchers for performance enhancement. This paper presents energy, environmental impact, and exergoeconomic (3E) analysis of transcritical CO2 booster and parallel compression supermarket refrigeration cycles based on meteorological data of 11 provinces in Türkiye as samples of different climatic regions. Parallel compression cycle achieved up to 18.4% higher coefficient of performance than booster cycle between the investigated ambient temperatures. Up to 5.6% annual energy consumption and environmental impact reduction were obtained using parallel compression. Unit product costs of the parallel compression cycles were calculated between 8.2% and 18% lower than booster cycle in investigated provinces. Developing energy-efficient systems that use environmentally friendly refrigerants will contribute to a sustainable future.

Potential assessment of biomass-based single-stage adsorption systems for refrigeration, cooling, and heat-pumping applications

ABSTRACT This article presents the performance estimation of a single-stage vapor adsorption system employing various carbon-based adsorbents with ethanol refrigerant, coupled with a small-scale biomass-based heating unit for space cooling, refrigeration, and heat-pumping applications. A detailed parametric investigation highlights the effects of operating temperatures, and heat exchanger to adsorbent mass ratio on specific cooling energy (SCE), coefficient of performance (COP), uptake efficiency (ηu), and mass of adsorbent to combustion fuel (mad/mcf) to identify the suitable adsorbent and sorption bed designs for each application. The numerical findings reveal that the flat-finned tube (FFT) adsorber outperforms traditional-finned tube (TFT) and tube & shell-type (T&S) adsorbers, achieving 19% and 30% higher COP, respectively, with biomass carbon-ethanol pair. The H2-treated Maxsorb-III shows the greatest optimal cooling COP (0.73), followed by the biomass-carbon (0.72) for refrigeration and space cooling. For heat pumping applications, biomass carbon-ethanol achieves the highest heat pumping COP (1.84) at a desorption temperature of 90°C, surpassing H2-treated Maxsorb-III. Further, the biomass-derived activated carbon requires the lowest amount of adsorbent per unit mass of combustion fuel in the biomass heating unit. The present thermodynamic analysis is a precursor for optimization of the potential heat-exchanger geometries and operating parameters, with the high-performance carbon adsorbents.

An efficient and eco-friendly heat-driven thermoacoustic refrigerator with bypass configuration

Developing high-efficiency and environmentally friendly cooling technology is crucial for sustainable life. Heat-driven thermoacoustic refrigerator (HDTR) is an emerging cooling technology characterized by no moving components, eco-friendly working substances, and high reliability. This study reports an innovative efficient HDTR with bypass configuration, which employs eco-friendly and economical working substances, the nitrogen and water. The bypass configuration enables good matching of acoustic power between the engine and cooler units at high heating temperatures, thus enhancing the efficiency. In addition, the employment of liquid resonator significantly reduces the working frequency and reduces the loss. An experimental investigation is performed on the onset characteristics and operating performance of the proposed system. The results show that a highest coefficient of performance (COP) of 0.49 and a cooling power of 726 W are achieved at the heating, ambient, and cooling temperatures of 500, 35, and 7 °C, respectively, exhibiting a high level for the HDTRs employing nitrogen. This work supplies an effective way to the efficiency enhancement of the HDTRs, indicating substantial potential of the proposed HDTR in eco-friendly air-conditioning applications.

The Analysis of Next-Generation Refrigerants in Terms of Energy, Exergy, and LCCP Perspective

In this study, commonly used hydrofluorocarbon (HFC)-based refrigerants R404A and R410A, as well as hydrofluoroolefin (HFO)-based environmentally friendly next-generation refrigerant R1234yf with a low global warming potential (GWP), were analyzed in terms of energy, exergy, and life cycle climate performance (LCCP) in refrigeration and air conditioning systems. All three refrigerants were examined at four different evaporation temperatures (-30°C, -15°C, -5°C, 0°C) with a constant condenser temperature of 50°C using a simulation program. For different evaporation temperatures, the performance of the refrigerants was evaluated using the first and second laws of thermodynamics, and performance coefficients, exergy efficiency, and exergy destruction were calculated. Additionally, the amount of kgCO₂e equivalent was calculated using the LCCP method. In the study, it was found that the compressor energy consumption of R410A and R1234yf refrigerants was similar and approximately 7% lower than that of the R404A refrigerant. The highest coefficient of performance (COP) value was determined for R1234yf. It was observed that R1234yf refrigerant had the highest exergy efficiency starting from -15°C. The kgCO₂e equivalent emission values calculated using the LCCP method revealed that R404A had the highest CO₂ emissions, while R1234yf had the lowest. Furthermore, based on the simulation study and theoretical calculations, it was determined that R410A and R1234yf refrigerants could be considered as alternative choices to R404A refrigerants in systems where two refrigerants are used.

Effect of overlapping and space between stages of a three-bladed double-stage Savonius hydrokinetic turbine for low flow speed perennial river application

ABSTRACT Savonius-like hydrokinetic turbine (SAHT) in low-speed flow streams of perennial rivers is not much explored. In this paper, a triple-bladed double-stage SAHT is designed, and its performance is investigated for low flow speeds within 0.45–0.65 m/s under the effect of blade overlapping (within 10–20% in each stage), turbine diameter (within 208–234 mm), and without and with space between the stages (5.0 mm) at different operating speed ratios. Different combinations of design and operating input parameters are studied to obtain a reliable assessment of SAHT performance. After analyzing the results, the best conditions of input parameters and output performance parameters are reported in their nondimensional forms for future use of the obtained results. The torque produced by the turbine increased with the applied brake load, leading to its maximum value at the highest brake load 0.83 times the maximum load. The highest coefficient of performance is obtained as 0.086 at a space 0.25 times the maximum space (i.e. 20 mm), overlapping 15%, brake load 0.83 times the maximum load, tip speed ratio 0.276. And for this, the corresponding power 0.85 times the maximum power (i.e. 0.201 W) at free-stream flow speed of 0.85 times the maximum flow speed (i.e. 0.65 m/s) is obtained. The present turbine with space and overlapping exhibits better performance than some available SAHT designs of single/double stage, two-blade/multi-blade with/without overlap configurations. The novelty of the work is that an improved SAHT has been developed for low-flow speed perennial river applications in the band of low tip speed ratios by combining design conditions like double-stage, space between stages, and overlapping.

CFD Analysis of Refrigerator Integrated with Atmospheric Water Generator

This Research article discuss about the study of performance analysis. This system is a combination of refrigerator and Atmospheric Water Generator (AWG). The purpose behind integrating two devices is to get benefit of both products together, refrigerator will act as a domestic refrigerator plus the atmospheric water system will generate the fresh distilled water to drink. This system is designed to generate a water of 20 liters per day. Also, it is designed in such a way that, this AWG can attach with various capacity is the refrigerator. Performance evaluation of this system is done with the help of computational fluid dynamics. Fluent module is used in ANSYS software. Various levels of parameter are evaluated, variables considered in the study were Relative humidity, velocity of air in AWG heat exchanger, and temperature of air. The output parameters evaluated like water generation capacity of AWG, Coefficient of Performance (COP) of AWG and refrigerator and heat exchanger efficiency. The results of CFD shows positive results as per design. 24th case has given highest COP 1.26. General, range of COP lie between 1.127 to 1.260. COP of Standard Refrigerator remain between 1.437 to 1.593. Also, it means COP of other two cases are more. As far as COP of Refrigerator concern, COP with AWG is heist i.e. 1.91. But it cannot be clearly state that, COP with AWG is more than COP without AWG.

Challenges and potentials of using a local heat pump in a 5 GDHC solution: Results from field and laboratory evaluations

In fifth generation district heating and cooling (5GDHC), the temperature range of the heat source is wider then in current common heat pump systems. The results of this study show that the heat pumps and chillers that are available in the market are not well adapted to 5GDHC applications due to the wide working range of 5GHDC. In order to maintain a high efficiency, current design parameters should be adjusted. This affects the dimensioning of all components in the refrigerant circuit and the required volume of refrigerant.An operational challenge specific to 5GDHC occurs when there is a low power demand at a relatively low temperature (eg. 35 °C) on the condenser side that coincides with a relatively high temperature (eg. 25 °C) on the evaporator side, resulting in a high thermal power during times with limited demand.Since the 5GDHC distributes both cooling and heating, it is also a challenge to successfully control the local heat pump in order that it fulfils the demands on both the hot and cold side. The heat pumps connected to 5GDHC systems have the potential to reach a high coefficient of performance (COP), due to the high temperature of the heat source. The challenge is to maintain a high COP throughout operation. At the ends of the heat pumps operational temperature range, the efficiency tends to drop considerably, resulting in a low System Efficiency Index compared to operations well within the operational range. This research seeks to address these challenges by highlighting better design principles in order to realize the untapped potential of 5GDHC systems. This is performed by investigating the influence of individual components on the performance of a local heat pump installed in a 5GDHC grid, assessed through theoretical simulations, field tests and laboratory measurements.

Investigation of the thermodynamic performance of a direct-expansion solar-assisted heat pump under very cold climatic conditions with and without glazing

This study investigates the long-term thermodynamic performance of a direct-expansion solar-assisted (DX-SAHP) system for hot water production in an average Canadian household. Performance is evaluated using realistic time-varying demand profiles and DX-SAHP with and without glazing under cold climatic conditions. A mathematical model for determining the system's long-term thermodynamic performance based on the first law of thermodynamics and heat transfer fundamentals is developed and thoroughly validated. The solution is implemented in MATLAB®. The CoolProp® database is coupled with MATLAB® and used to determine the working fluid's thermal physical properties. Besides, the thermodynamic performance of the DX-SAHP throughout the year, operating with low global warming potential (GWP) and class A safety refrigerants, was evaluated. Moreover, the influence of solar irradiation and ambient air temperature on the DX-SAHP's thermodynamic performance is studied. Results indicate that the monthly average coefficient of performance (COP) varies between 2.5 and 3.8, while the monthly average energy consumption of the system varies between 170 and 275 kWh. The obtained figures for COP and power consumption demonstrate the high-efficiency potential of the DX-SAHP system, making it an attractive alternative to reduce energy costs and CO2 emissions in residential water heating. In addition, results show that R1233zd gives the highest COPs, followed by R152a, R1234ze, R134a, R1234yf and R32. Besides, the long-term simulation results indicate that the DX-SAHP water heater without glazing has superior thermal performance compared to one with glazing. Also, results show that the COP rises as the ambient temperature or solar radiation level increases.

Thermo-hydraulic performance evaluation of radial tree-branching microchannel heat sinks for electronic cooling applications

The fractal-like tree-branching microchannel heat sink (TB-MCHS) can be a potential solution for the cooling of electronic devices due to its ability to dissipate high heat flux and maintain uniform temperature distribution on the chip surface while requiring lower pumping power compared with the conventional TB-MCHS with constant channel depth. This work proposed a novel design of radial TB-MCHS with continuously varying, either increasing or decreasing, channel depth from the centre inlet to the radial outlet, resulting in different fluid volumes in channels compared to the conventional constant channel height TB-MCHS. A three-dimensional numerical model is developed and validated with in-house experimental results to study the thermo-hydrodynamic performance and entropy generation of the TB-MCHSs. The results reveal that the proposed designs of TB-MCHS with different fluid volumes negligibly enhance the heat transfer coefficient and significantly reduce the pressure drop and pumping power requirement compared to that of constant fluid volumes. The TB-MCHS with continuously increasing channel depth (TB-MCHS-DIV) exhibits the lowest pressure drop, thermal resistance, substrate temperature, and entropy generation among all the designs of TB-MCHS considered. However, the TB-MCHS-DIV shows the lowest convective heat transfer coefficient and higher coefficient of performance (COP) and heat removal rate than the TB-MCHS-ST. Further, it is found that the TB-MCHS-DIV can be performed better than TB-MCHS-CON and TB-MCHS-ST at constant pumping power.

Exergy and energy analysis of a hybrid natural Gas/Hydrogen liquefaction cycle combined with methanol production plant

This paper presents an innovative renewable multi-generation system designed to simultaneously produce various fuels, including biomass-based methanol, liquid hydrogen, and liquid natural gas. This system is part of a broader strategy aimed at streamlining different processes within a comprehensive plant, enabling the simultaneous production of multiple biomass-based fuels at a single location. The implementation of this system in regions where natural gas liquefaction plants coexist with abundant forest resources allows for the efficient production of all required fuels. In this process, a new configuration leverages to regenerate the waste heat of methanol synthesis process in the diffusion absorption refrigeration cycle integrated to the natural gas liquefaction process to maximize energy and exergy efficiencies. Additionally, three hydrogen liquefaction processes are evaluated to identify the most suitable option based on performance, efficiency, and power consumption. The investigations reveal that the combined mixed refrigerant cycle (CMRC) emerges as the ideal choice for hydrogen liquefaction process, characterized by lower power consumption and a higher coefficient of performance. The energy and exergy efficiencies of biomass gasification and methanol synthesis processes are 87.54% and 80.41%. The energetic coefficient of performance of the natural gas liquefaction process and CMRC is 0.9 and 0.2209. The specific power consumption of natural gas liquefaction process is 0.225 kWh/kgLNG, and the specific power consumption of CMRC is 5.462 kWh/kgLH2. The natural gas liquefaction process is responsible for the highest portion of the total exergy destruction, with 32%.