Refrigeration Cycle Research Articles

Genetic algorithm-based optimization of combined supercritical CO2 power and flash-tank enhanced transcritical CO2 refrigeration cycle for shipboard waste heat recuperation

The shipping industry significantly contributes to global trade and economy, but is also responsible for approximately ∼3 % of global greenhouse gas (GHG) emissions. Harnessing waste heat from marine vessels to perform useful work is a potential solution to reduce these emissions. Although the Organic Rankine Cycle (ORC) and CO2 cycles have been studied separately for waste heat recovery, a combined power and refrigeration systems, utilizing both cycles have not been reported. Herein, a combined system, “Marine Energy Recovery System (MERS)”, that integrates the supercritical CO2 Brayton power cycle with a flash-tank-enhanced transcritical CO2 refrigeration cycle, is proposed, aiming to generate power and provide cooling simultaneously. The power cycle incorporates an ORC, and a flash-tank is introduced within the refrigeration cycle to improve system performance. Both cycles share a low-temperature recuperator and a gas cooler to further utilize the heat between them. The MERS is evaluated from both a 1st and 2nd law perspective against various performance metrics under different operating conditions, such as: gas cooler pressure, evaporation temperature, and turbine inlet temperature and pressure. Results elucidated that the MERS achieved energy and exergy efficiencies of 54.62 % and 54.90 %, respectively, representing significant improvements over similar systems. The net work output improved by 717.55 kW and the net cooling capacity by 515.7 kW relative to the reference system. Furthermore, a COP of 2.99 outlines its potential as a cooling system. To further enhance MERS’s performance, a multi-objective optimization approach is employed, utilizing Artificial Neural Network (ANN) and Genetic Algorithm (GA). Optimal operational conditions yielded an energy efficiency of 74.95 % while maintaining a net work output of 6890.55 kW with gas cooler pressure, turbine inlet temperature, and gas cooler outlet temperature being 9.5 MPa, 461.76°C and 50°C respectively. These findings support the reliability and improved design of the MERS for future marine applications.

Economic/sustainability optimization/analysis of an environmentally friendly trigeneration biomass gasification system using advanced machine learning

The present research presents an innovative thermal integration model for a biomass-based power plant to generate power, coolant, and liquefied hydrogen. This integrated arrangement comprises biomass gasification, gas turbine cycle, organic flash-bi-evaporator refrigeration cycle, multi-effect desalination, solid oxide electrolyzer, and Claude cycle. The selection of an eco-friendly fluid for the electricity-cooling production cycle is conduced relying on a comparative analysis. The subsequent examination evaluates the economic-sustainability performance criteria through sensitivity and contour analyses. The comparative assessment identifies R1234ze(Z) as the most suitable working fluid. Four objective functions are scrutinized, and two optimization scenarios are devised based on a machine learning approach using artificial neural networks and a multi-objective gray wolf optimization technique. In Scenario A, the focused objectives are the total destructed exergy and the cost of producing liquefied hydrogen. Meanwhile, Scenario B integrates the sustainability index and the overall system cost rate as primary criteria. Scenario A exhibits more favorable operational conditions and outcomes than scenario B, showing the objectives mentioned as 9955 kW and 3.25 $/kg, respectively. In this scenario, the sustainability index, the overall investment cost rate, and the net present value are obtained to be 1.74, 236 $/h, and 205 M$, correspondingly.

Thermodynamic characteristics of a novel solar single and double effect absorption refrigeration cycle

Solar absorption refrigeration systems provide one of the economical options for air conditioning. In order to reduce the complexity and economic cost, a more advanced solar single-double-effect switching system is proposed. The innovation of this system is that it replaces the single-effect and high-pressure generators in previously developed single-double-effect switching system with a specific generator. The optimal heat source switching temperature of the new system was determined by the genetic algorithm to be 125.5 °C. Compared with the original single-double-effect switching system, the average coefficient of performance of the system is increased by 8.6 %, and the fluctuation of refrigeration capacity during the switching period is reduced by 48 %. The new solar single-double-effect switching system is investigated based on thermodynamic characteristics, energy, exergy, and economy aspects. The results showed that heat exchangers of the system have strong coupling. The cooling water temperature has a greater impact on the performance of the dual-effect mode. In the single-effect mode, the special-pressure generator has the largest exergy destruction (39 %), while in the double-effect mode, the absorber has the largest exergy destruction (41 %). Besides, the economic analysis demonstrated that the new system is economically viable with a payback period of 9.33 years.

Analysis of intermediate cooling systems for CO2 compression trains of offshore oil wells

A multi-stage compression train with intermediate cooling used to inject carbon dioxide (CO2) in a well is modeled using two distinct configurations, direct and assisted cooling. The main difference between these configurations is that, in the latter, the process water responsible for the intermediate cooling is cooled down by a refrigeration cycle. These configurations are thermodynamically modeled while aiming to investigate the effect of key parameters on two main variables: (i) the overall global conductance and (ii) the overall power consumed by the compressors and auxiliary cooling systems. The results for direct cooling indicate that the power consumed by the compression train is inversely related to the global conductance, while an increase in the number of intermediate compression stages also reduces the global conductance. The assisted cooling, which considered 20 different working fluids for the refrigeration cycle, presented a minimal value for the global conductance for a given value of the overall power consumed by the compressors (train and refrigeration cycle). Finally, a comparison between both configurations reveals that while direct cooling offers a better compromise solution between global conductance and power consumption, assisted cooling can produce a significant reduction of global conductance.

Enhancing thermodynamic performance with an advanced combined power and refrigeration cycle with dual LNG cold energy utilization

Utilizing waste heat to drive thermodynamic systems is imperative for improving energy efficiency, thereby improving sustainability. A combined cooling and power systems (CCP) utilizes heat from a temperature source to deliver both power and cooling. However, CCP systems utilizing LNG cold energy suffers from low second law efficiency due to significant temperature differences. To address this, an “Advanced Power and Cooling with LNG Utilization (ACPLU)” system is proposed, integrating a cascaded transcritical carbon dioxide (TCO2)-LNG cycle with an Organic Rankine cycle (ORC) for improved power generation and an absorption refrigeration system (ARS) for simultaneous cooling. This study evaluates the second law efficiency, net work output, and exergy destruction performance through a sensitivity analysis, optimizing variables such as heat source temperature, superheater temperature difference, ORC and CO2 turbine inlet and condenser pressures, evaporator temperature, and pinch point temperatures of heat exchangers and generator. Compared to previous studies on CCP systems, the ACPLU shows a superior performance, with a second law efficiency of 27.3 % and a net work output of 11.76 MW. Cyclopentane as an ORC working fluid resulted in the highest second law efficiency of 29.06 % and net work output of 12.27 MW. Parametric analysis suggested that heat source temperature significantly impacts net power output. The exergy analysis concluded that a high-pressure ratio and good thermal match between the heat exchangers enhance overall performance. Utilizing artificial neural network (ANN) to produce a multiple-input-multiple-output (MIMO) objective function and performing multi-objective optimization (MOO) using genetic algorithm (GA), an improved second law efficiency and net power output by 28.11 % and 14.16 MW respectively, with pentane as the working fluid, is demonstrated. An average cost rate of 9.121 $/GJ was observed through a thermo-economic analysis. The ACPLU system is promising for medium temperature waste heat recovery, such as, pharmaceutical manufacturing plants.

Dynamic evaluation of a vapor compression refrigeration cycle combined with a PCM storage tank for improving condenser performance

In this study, a vapor compression refrigeration cycle integrated with a phase change material (PCM) storage tank has been dynamically simulated over a 24-h period. The primary objective of this system is to reduce electric energy consumption during on-peak hours (12:00–19:00) and shift it to off-peak hours (1:00–10:00). During off-peak hours, the vapor compression refrigeration system stores cooling energy in the PCM storage tank. The stored cooling energy is then reused during on-peak hours to pre-cool the condenser inlet refrigerant, enhancing the cooling system's performance and reducing electric consumption during on-peak hours. Oleic acid, eutectic mixtures of 45 % capric acid and 55 % lauric acid by weight (CL), a commercial blend of salt hydrate and paraffin wax (SP224A), and CaCl2.6H2O have been selected as the PCM mediums. The effects of weather conditions and PCM storage tank parameters on the system's performance have been investigated. The results indicate that SP224A performs the best in most weather conditions. The maximum electric peak load shaving occurred under Ramsar city weather conditions, achieving 98.85 %. Additionally, the compressor's electric energy consumption is reduced by about 23.38 %. Moreover, increasing the length of PCM storage pipes leads to a reduction in compressor energy consumption during on-peak hours, as well as electric peak load shaving, with an improvement of up to 156 %.

Expression of Concern for article entitled “Improving the performance of a lithium-ion battery connected to a solar system using a nano-refrigerant in an ejector refrigeration cycle”

Expression of Concern for article entitled “Improving the performance of a lithium-ion battery connected to a solar system using a nano-refrigerant in an ejector refrigeration cycle”

Performance Evaluation of Novel Advanced Recompression Absorption Refrigeration Systems Equipped with Ejector and Vapor Injection Technology

The absorption refrigeration cycle (ARC) faces challenges considering its decreased working pressure and COP. By integrating Recompression technology (RAC) into ARC, these issues are partly addressed. To address these inefficiencies, in this study, ejector and vapor injection techniques are incorporated into refrigerant side of the RAC cycle, resulting in the development of advanced systems: Refrigerant ejector enhanced recompression absorption cycle (RE-RAC) and Vapor injection enhanced recompression absorption cycle (VI-RAC). Key metrics assessed are 1st and 2nd law efficiency, system exergy destruction rate, compressor load, and generator heat requirements. Conclusively, under analogous operating conditions, RE-RAC and VI-RAC demonstrate a substantial improvement in COP, achieving 76 % and 63 % enhancements, respectively, over the standard RAC system. Compared to the conventional solution ejector-based SE-RAC, these systems show performance increases of 28 % and 19 %, respectively. The findings also highlight the sensitivity of these systems to parameters such as generator temperature and pressure, evaporator temperature, absorber temperature, evaporator recovery and normal pressure ratio. At higher evaporator temperature and lower generator temperature, the performance of these systems as well as enhancement of RE-RAC over VI-RAC is higher observed. The optimal value of generator pressure and recovery pressure ratio for maximum efficiency and minimum total exergy destruction rate is also dependent upon these. At a generator temperature of 67 °C and an evaporator temperature of 8 °C, RE-RAC exhibits a 35 % higher COP compared to VI-RAC. However, at −10 °C evaporator temperature, changes in external generator heat input and compressor work reduce the COP enhancement to 5 %.

Optimization and analysis of a novel hydrogen liquefaction coupled system with dual path hydrogen refrigeration cycle and the closed nitrogen cycle pre-cooling

The high cost and inefficiency of the hydrogen liquefaction process have impeded the growth of the liquid hydrogen industry. Through the analysis of existing hydrogen liquefaction systems, a novel compact hydrogen liquefaction system that can reduce energy consumption is developed. The system comprises a closed cycle of nitrogen pre-cooling process and dual hydrogen refrigeration cycle cryo-cooling process that are integrated to form and create the coupled system. To evaluate the performance of the proposed hydrogen liquefaction system, an independent system is additionally constructed for comparative analysis, which separates the pre-cooling process and cryo-cooling process. The parameters are optimized using a genetic algorithm for both independent and coupled systems. The results show that the specific energy consumption, coefficient of performance and exergy efficiency of the coupled system are 11.41 kWh/kgLH2, 0.12 and 26.1%, respectively. Furthermore, the coupled system demonstrates significant performance, where the useful and recoverable exergy of the coupled system surpasses that of the independent system. The coupled system's exergy destruction and total UA values decrease by 7.25% and 40.93%, respectively. Moreover, the economic evaluation shows that the total annual cost of the coupled system is $6.22 million per year. The total system cost is sensitive to the electricity price, and the operating expenditure as a percentage of total annualized cost increases from 16% to 53% when the operating electricity price increases from $0.01 to $0.06. This study aims to support the practical development of future hydrogen liquefaction systems by optimizing the cooling system structure.

Thermo-economic investigation on organic Rankine cycle based solar integrated ejector-trigeneration system (EORC-CCHP) for Indian climate

A novel solar integrated ejector-based combined cooling, heating, and power (EORC-CCHP) system based on an organic Rankine cycle is proposed to provide sustainable multiple outputs to meet energy demand. A comprehensive energy and exergy analysis is performed to evaluate the system's performance using six different environment-friendly refrigerants, such as R1233zd, R245fa, R236fa, R142b, R600a, and R124. A parabolic trough collector (PTC) distributes the solar energy to the boiler as a heat source. To study the system's performance at sub-zero evaporator temperatures, the primary flow from the ORC turbine's first-stage expansion is extracted and sent through an ejector refrigeration cycle for the required cooling effect. The remaining refrigerant is expanded across the turbine with a targeted power output of 5 kW and is sent for heat recovery across the heater. Among the refrigerants studied, R600a, R124, and R1233zd demonstrated the highest refrigeration COP of 0.58, system COP of 1.69, and exergy efficiency of around 68.26%. However, due to the lower critical condenser temperatures of R124 and R1233zd makes them obsolete due to negative pressure, R600a is observed as the optimal working fluid. The PTC system demonstrates diurnal variations, with a combined peak energy output of 31.3 kW in May for the Hyderabad climate. Exergy analysis shows that the primary sources for exergy destruction are the PTC system, boiler, and ejector, with destruction rates of 51%, 20.1%, and 22.1%, respectively. The boiler is the main source of exergy destruction cost, with a cost of 0.18 $/h, and the condenser and PTC exhibit the highest total cost rates. The environmental impact of the PTC system is assessed, with July showing the highest environmental effect to unit useful exergy of 71.54 mPts/GJ.

Cryogenic-membrane separation process for helium extraction and ethane co-production from natural gas

In order to address the defects of high energy consumption and low efficiency in the single cryogenic separation process for helium extraction, this paper integrate post-expansion nitrogen cycle refrigeration with membrane separation to establish a novel natural gas cryogenic-membrane helium recovery process. Based on four mainstream processes for ethane recovery from natural gas, an optimal ethane recovery method is selected and incorporated into the proposed cryogenic-membrane helium recovery process. The process is then simulated using ASPEN HYSYS software. The effects of operating parameters on critical equipment energy consumption, helium product concentration and ethane recovery were evaluated. The simulation results indicate that in the proposed helium recovery process, the concentration of refined helium reaches 99.6 %, and the ethane recovery rate is 90.13 %. Compared to the single helium extraction process, the total compressor energy consumption in our process is reduced by 23.10 %, and the integrated energy consumption is reduced by 20.4 %.

Waste heat recovery from a green ammonia production plant by Kalina and vapour absorption refrigeration cycles: A comparative energy, exergy, environmental and economic analysis

The production of green ammonia involves significant energy penalties due to heat losses. Recovering this heat can enhance the sustainability of ammonia production. However, this area remains largely unexplored, making it unclear which approach to waste heat recovery is best suited. Therefore, this paper investigates two methods of waste heat recovery in a green ammonia production plant: the Kalina Cycle (KC) and the Vapour Absorption Refrigeration Cycle (VARC). The underlying processes are simulated, and an analysis is conducted covering energy, exergy, environmental, and economic aspects. The results show that integrating the system with KC yields a marginal energy efficiency improvement of about 1%. However, when the conventional ammonia production system is integrated with VARC, the improvement in energy efficiency reaches 8%, while exergy efficiency improves by 11%. An environmental assessment estimates the greenhouse gas emissions saved by each heat recovery method, revealing that VARC achieves almost four times the emission savings compared to KC. Economically, integrating KC increases the levelized cost of ammonia (LCOA) by over 18%, whereas adding VARC has almost no impact on the LCOA. Overall, the co-production of refrigeration using VARC is identified as a superior heat recovery technique for green ammonia plants.

Gravity refrigeration cycle: An efficient approach for refrigeration in mountainous regions

Traditional refrigeration methods often rely on energy-intensive, high operational costs and result in considerable negative environmental impacts. This paper introduces a novel and revolutionary approach to refrigeration technology through the implementation of the Gravity Refrigeration Cycle (GRC). GRC utilizes vertical pipelines in high elevation mountains instead of compressors to increase the pressure of refrigeration gases. Gas added to the top of the vertical pipeline is pulled down by gravity, increasing the pressure and density of the gas along the vertical pipeline and liquefying it at the bottom of the pipeline. The liquid is then transported back to the top of the mountain, where cooling services are provided, and the cycle starts again. The estimated coefficient of performance for a GRC system with 28 and −7 °C hot and cold sinks is 4.19, which is 1.84 times higher than conventional, mechanical refrigeration systems and a cost of 274 USD/kWt, 2.2 times higher than conventional systems. Gravity Refrigeration Cycle represents a paradigm shift in refrigeration technology in mountainous regions, particularly for processes with high demand for cooling, such as hydrogen liquefaction. As the world seeks greener and more economical alternatives, GRC could be a promising advancement in refrigeration.

Integration of the single-effect mixed refrigerant cycle with liquified air energy storage and cold energy of LNG regasification: Energy, exergy, and efficiency prospectives

The escalating global energy demand has prompted increased focus on the industry of liquefied natural gas (LNG), emphasizing the need for optimizing liquefaction processes to minimize capital costs. Thus, the integration between liquified natural gas LNG regasification and liquid air energy storage (LAES) to produce electricity and utilize the cold energy of LNG regasification has several interests to maximize the benefits of the process to generate power and face the challenges such as energy saving and reducing the total operations costs … etc. Fortunately, this study introduces a novel approach that combines a single-effect mixed refrigerant (SMR) cycle with air liquefaction, incorporating regenerative Rankine cycles for enhanced efficiency. The effectiveness of the LNG-SMR-LAES process was evaluated using comprehensive energy, exergy, and economic analyses to ascertain its viability. The results showed a notable improvement in the overall net power energy by 6 % and an increase in exergy efficiency by 11.7 % compared to the base case. Energy savings of 31.6 % (470.10 kW) contributed to the process's environmental and economic feasibility. The net present value was estimated at 11,230.4 US dollars, affirming the industrial-feasible design and economic viability of the LNG-SMR-LAES process.

Energy, exergy, environmental (3E) analyses and multi-objective optimization of vortex tube coupled with transcritical refrigeration cycle

The present study deals with the thermodynamic investigation of vortex tube coupled with trans-critical vapour compression refrigeration cycle (TVTC), followed by environmental analysis and multi-objective optimization. In this research, effect of various operating and design parameters is studied on the performance of TVTC. Furthermore, a comparison is made between the outcomes of TVTC and simple trans-critical vapour compression refrigeration cycle (TVCR). Results show that the optimum gascooler pressure for TVTC is observed to be lower than that of TVCR. Also, the cooling capacity and COP of TVTC are observed to be 10.1 % to 21.1 % and 2.3 % to 11.3 %, respectively, greater than those of TVCR. Moreover, the exergetic efficiency of TVTC is 2.3 % to 11.3 % higher than that of TVCR for the investigated range of evaporator and gascooler exit temperatures. The environmental penalty cost (per unit cooling capacity) of TVTC is 3.5 % to 12.2 % lower than that of TVCR. Furthermore, the coefficient of structural bond is calculated in order to choose the most sensitive parameters for system's performance. Additionally, genetic algorithm-based multi-objective optimization has been performed, with the evaporator temperature serving as the primary determining factor in establishing the optimal solution. This finding can guide the development of TVTC-based systems for a wide range of applications.

Modeling and performance assessment of a combined geothermal-ejector refrigeration system

This study investigates the integration of an innovative combined power and cooling (CPC) system into the existing infrastructure of the DORA 1 geothermal power plant in Aydın, Turkey. Using real operational data, this research models the integration of an ejector refrigeration cycle to enhance both power generation and cooling capabilities. The proposed system utilizes waste heat from the geothermal power plant's re-injection wells, which operate at temperatures of 81.7 °C and 69.1 °C. Four environmentally friendly refrigerants (R290, R717, R600 and R1234ze) were evaluated for their performance in the refrigeration cycle. Of these, R717 and R1234ze showed superior performance, achieving the highest coefficients of performance (COPs) and exergy efficiencies. The integration of the ejector refrigeration cycle resulted in a 12 % improvement in overall energy efficiency compared to traditional power-only systems, with a maximum COP of 0.72 under optimal conditions. This study fills a significant research gap by providing a practical application of combined geothermal power and refrigeration, and provides valuable insights into the feasibility, efficiency and sustainability of such systems. The results suggest that the proposed system not only improves energy utilization, but also contributes to environmental sustainability by reducing reliance on conventional cooling methods. This research has the potential to guide future developments in the field of geothermal energy and refrigeration, promoting the adoption of integrated energy systems for improved efficiency and reduced environmental impact.

4E analysis for a novel cryogenic hydrogen liquefaction process using various refrigerants: Energy, exergy, economic, and environment

Hydrogen liquefaction process (HLP) is a principal technology to overcome energy storage and transportation problems and to meet the demand for an eco-friendly energy source. This study proposes three conceptual designs of HLPs with various refrigerant cycles. The specific energy consumption (SEC) of HLP could be reduced by various refrigerants. Three different refrigerants (liquid air (LA)), liquified natural gas (LNG), and mixed refrigerants (MR)) were compared to the conventional LN2-based HLP to verify 4E (efficiency, exergy, economics, and environmental) of each process based on their thermodynamic properties. From the results, we found that the process performance, economics, and environmental effects of the LNG-based hydrogen liquefaction process (LNG-HLP) were the best. In particular, the LNG-HLP, which uses the cold energy of LNG, required less refrigerant than LN2, thereby reducing the energy consumed by major compressors. It had an SEC of 11.04 KWh/kg-LH2 and capital, operating cost, and CO2 emissions of the LNG-HLP process were considerably lower by 5.5 %, 6.2 %, and 12.2 % (unit kg CO2eq/kg LH2), respectively, compared to the conventional process. To propose better economic or environmental scenarios to stakeholders and governments, in this study, the HLP and hydrogen production processes were expanded to include CO2 emission calculation and carried out analysis for levelized cost of hydrogen contribution rate to electricity production types by country.

Refrigeration by modified Otto cycles and modified swaps through generalized measurements

We introduce two types of thermodynamic refrigeration cycles obtained through modification of the Otto cycle refrigerator by a generalized measurement channel. These refrigerators are corresponding to the activation of the measurement-based stroke before (first type) and after (second type) the full thermalization of the cooling medium by the cold reservoir in the related familiar Otto cycle. We show that the coefficient of performance for the first type modified refrigerator increases linearly in terms of measurement strength parameter, beyond the classical cooling of the familiar Otto cycle refrigerator. The second type interestingly introduces an autonomous refrigerator whose supplying work is provided by a quantum engine induced by the measurement channel and operates simultaneously inside the modified cycle. By the considered measurement channel, we also establish such modifications on the swap refrigerator. It is observed that the thermodynamic properties of the obtained modified swap refrigerators are the same as of the modified Otto cycle ones respectively.

Investigation on hourly characteristics of solar absorption refrigeration cycle integrated with a dual-cooling grade-compression cycle

Solar absorption refrigeration cycle consumes almost no electricity, but its low refrigeration efficiency and intermittent operation issues need addressing. Based on the viewpoint of cold energy grade production matching air-conditioning cooling load grade, a solar absorption refrigeration cycle integrated with a dual-cooling grade-compression cycle (SARC-DGC) is proposed to boost the solar utilization and achieve all-weather cooling, which includes solar absorption refrigeration (SAR) subsystem, subcooled water circulating (SWC) subsystem and dual-cooling grade-compression refrigeration (DGR) subsystem. The simulation models of proposed cycle are developed by lumped-parameter and distributed-parameter methods, and the simulation results are validated with experimental results. The hourly characteristics of SARC-DGC cycle on a typical day are evaluated and compared with those of the conventional solar absorption refrigeration (SAR) cycle and air-cooled compression refrigeration (ACR) cycle. The results show that the hourly cooling performance of SARC-DGC cycle is well matched with the building cooling load demand, so as to realize the cold energy grade production and utilization. The working hours of SAR subsystem are 42.86 % longer than that of conventional SAR cycle, with a 31.92 % increase in daily cooling capacity, while the daily power consumption of the proposed cycle is on average 27.31 % lower than that of conventional ACR cycle.

Hydrogen pressure-based comparative and applicability analysis of different innovative Claude cycles for large-scale hydrogen liquefaction

The Claude cycle is the preferred option for large-scale hydrogen liquefaction. However, the thermophysical properties of hydrogen vary substantially around the critical temperature and are strongly affected by hydrogen pressure. This leads to the fact that the classic Claude cycle is not universal for hydrogen at different pressures. Three innovative Claude cycles have been proposed. The applicability of three hydrogen liquefaction cycles is evaluated from specific energy consumption (SEC) perspective. The classic Claude cycle (Cycle 1) is suitable for the liquefaction of hydrogen with pressure above 3500 kPa, and the SEC for the liquefaction of hydrogen at 3500 kPa is 5.02 kWh/kgLH2. The Claude cycle (Cycle 2) with two cross-arranged refrigeration cycles is suitable for hydrogen with pressure between 2200 and 3500 kPa, and the SEC is 4.98 kWh/kgLH2 for the liquefaction of hydrogen at 2500 kPa. The Claude cycle (Cycle 3) with a split-flow refrigeration cycle is suitable for hydrogen with pressure less than 2200 kPa, and the SEC for the liquefaction of hydrogen at 1500 kPa is 5.27 kWh/kgLH2. Furthermore, the reasons for the SEC and applicability of three cycles being affected by hydrogen pressure are investigated by means of parametric analysis, heat exchanger performance analysis, and exergy analysis.