Pre-cooling System Research Articles

Performance analysis of precooling systems for cryogenic carbon capture: A comparative study of theoretical, numerical, and experimental methods

The urgency of addressing climate change has necessitated innovative and practical approaches to reducing greenhouse gas emissions. Cryogenic Carbon Capture (CCC) technology has emerged as a promising solution for capturing CO2 from industrial emissions. This study investigates a simplified design for a precooling system within CCC technology, focusing on optimizing the efficiency and reliability of the system while minimizing energy consumption. The research examines the effects of CO2 concentration in a gas mixture (simulated flue gas, nitrogen and carbon dioxide), cooling bath temperature, and gas mixture flow rate on the performance of heat exchangers in the precooling system. Theoretical, numerical, and experimental analyses were conducted to assess the system's performance. The use of liquid nitrogen at −196 °C in the cooling bath was found unsuitable due to CO2 freezing within the pipes. Instead, a mixture of dry ice and isopropyl alcohol at −78.5 °C proved effective in maintaining consistent temperature and pressure conditions without causing CO2 blockages. Numerical simulations highlighted the importance of optimizing pipe length to balance temperature control and pressure dynamics, with a 140 cm pipe length identified as optimal for heat exchanger design. Experimental results revealed that longer pipes enhance cooling performance due to increased heat exchange surface area, while higher CO2 compositions and flow rates result in higher outlet temperatures and pressures. The study emphasizes the need for further research and simulation work to refine heat exchanger designs for industrial applications, aiming to develop systems that maximize cooling efficiency while ensuring reliable operation.

ANÁLISIS DEL COMPORTAMIENTO Y OPTIMIZACIÓN DE UN SISTEMA DE AIRE ACONDICIONADO SOLAR CON PRE-ENFRIAMIENTO DEL AIRE DE ENTRADA AL CONDENSADOR MEDIANTE ATOMIZACIÓN POR ULTRASONIDOS.

The most directly applicable strategies for improving the performance of air conditioning systems are the use of renewable energy sources and improving their efficiency by lowering their condensing temperature. An emerging area of study is the use of ultrasonic equipment to improve the efficiency of a wide variety of processes, with interesting results in the field of evaporative pre-cooling. The present study aims to analyse and optimise a conventional split-type solar cooling system driven by photovoltaic energy, which has a hybridisation of the condenser using ultrasonic atomisers to improve its efficiency. An experimental study has been carried out for different configurations of active atomisers, with the aim of modelling the behaviour of this system under different operating conditions. The annual energy results for different locations will be analysed and the control criteria of the ultrasonic pre-cooling system will be optimised according to the operating conditions.

액체 수소 생산을 위한 예냉 시스템의 수소 가스 예냉 온도 및 열 교환기 면적에 관한 연구

액체 수소 생산을 위한 예냉 시스템의 수소 가스 예냉 온도 및 열 교환기 면적에 관한 연구

Enhancement of the precooling system performance for aviation engines by volatile liquid injection

Water injection precooling in aviation engines is a promising technique that can enhance performance, improve efficiency, and reduce emissions, especially at high altitudes and Mach numbers. However, its implementation in aviation engines requires careful engineering and design considerations due to the restricted space available for installation and operation, as well as the challenges posed by high inlet air velocities. Therefore, the present study experimentally and numerically evaluates the effectiveness of spray precooling for jet engines and introduces novel insights into optimizing droplet dynamics and nozzle configurations in short, narrow spray ducts under high inlet air temperature and velocity. The impact of water spray cooling on the uniformity of inlet air is also investigated for nonuniform air temperature conditions, which has yet to be mentioned in previous research. An experimental configuration has been devised and implemented to investigate water injection precooling within a rectangular spray duct. The evaporative cooling process through the spray duct and the injected droplet trajectories were predicted using an Eulerian-Lagrangian computational fluid dynamics (CFD) model. The CFD model was verified using the present experiments, and there is a strong correlation between the experimental data and simulation findings, with an average discrepancy of less than 7%. The effectiveness of the water injection system is investigated at different operating parameters such as nozzle arrangements, coolant type, droplet size, and variable velocities. The results showed that sprays characterized by small mean diameters and high initial droplet velocity significantly enhance spray cooling performance. Changing the nozzle configurations impacts spray cooling performance considerably, with the cross-outside case providing the best results. Notwithstanding its advantageous evaporation rate, introducing methanol via injection does not yield significant enhancements. Water injection is crucial in achieving a more homogeneous temperature distribution by reducing temperature disparities and promoting mixing and evaporation.

Design and Economic Analysis of a Solar Thermal Pre-Cooling System for Agro-Cold Chain in Lesotho

The agricultural sector in Lesotho grapples with significant challenges regarding post-harvest losses. Given that 40% of all agricultural products require cold storage, food quality is compromised due to lack of cold storage to extract the heat from exposure to high field temperatures after harvest. This research proposes a solar thermal cooling system tailored to the specific needs of preserving fresh agricultural produce, leveraging Lesotho’s abundant solar energy resources. Through TRNSYS simulation and MATLAB economic analysis, optimal system parameters are determined, ensuring both technical efficiency and financial viability. The outcomes indicate that the proposed absorption solar thermal cooling system, incorporating evacuated tube collectors and an auxiliary boiler, effectively manages a cooling load of 7.318 kW, preserving fresh vegetables at 6.1°C. The optimized design features a chiller with a Coefficient of Performance of 0.8, a collector area of 12 m², and a hot storage volume of 0.2 m³, maximizing solar energy utilization. Importantly, economic metrics such as Levelized Cost of Energy ($0.085/kWh), Net Present Value ($9,200), Discounted Payback Period (12 years), and Savings to Investment Ratio (achieving 1 in year 13) demonstrate the financial feasibility and profitability of the system. These findings underscore the potential of solar thermal cooling as a promising investment option for addressing refrigeration needs in Lesotho, offering a sustainable solution to mitigate post-harvest losses and enhance economic performance in the agricultural sector.

Study on a novel hydrogen liquification process applying mixed-refrigerant for pre-cooling and cryogenics

Reducing the energy consumption of hydrogen liquefaction process is an urgent issue to improve the economy of liquid hydrogen transportation. A novel large-scale hydrogen liquefaction system, with a capacity of 100 TPD, is proposed in this paper. The pre-cooling system is composed of a mixed-refrigerant (MR) refrigeration cycle and a CO2–NH3 cascade refrigeration cycle. Due to the auxiliary pre-cooling effect of the CO2–NH3 cascade cycle, temperature of the pre-cooled hydrogen can be as low as −200.9 °C. A modified MR Joule Brayton cycle with an additional compressor is used as the cryogenic system to cool the hydrogen from −200.9 °C to −252.2 °C. Besides, a four-stage ortho-to-para conversion (OPC) process is utilized. Performance of the novel system is investigated and optimized using the Aspen HYSYS software. According to the results, the lowest specific energy consumption (SEC) of the proposed process is 6.15 kWh/kgLH2 and the exergy efficiency is as high as 67.4%. Based on the energy analysis, the best system coefficient of performance is 0.1751 with a 96.3% of p-H2 in the liquid hydrogen. In addition, compared to the initial conceptual system, the proposed system exhibits significant performance enhancements, a 20% reduction in SEC and a 27.9% increase in exergy efficiency. A sensitivity analysis is conducted to assess the impact of refrigerant composition and hydrogen pressure on the system, resulting in the determination of the optimal proportions of refrigerant components and the optimal inlet pressure. Results of the study can provide theoretical reference for the further development of large-scale hydrogen liquefaction technology.

Intercomparison of Efficacy of Transcutaneous Electrical Nerve Stimulation and Precooling Vibration Device on Pain and Anxiety Management during Administration of Local Anesthesia Injection in 6-12-year-olds.

To compare and evaluate the efficacy of transcutaneous electrical nerve stimulation (TENS) and a vibrational precooling system in reducing pain and anxiety during the administration of local anesthesia in children aged 6-12 years old. A total of 60 children aged 6-12 years old participated in this randomized controlled trial and were randomly allocated to three groups: the conventional method group, the vibrational precooling system group, and the TENS group. The Modified Dental Anxiety Scale (MDAS), pulse rate, and oxygen saturation were recorded to assess the preoperative anxiety of the participating children. Sound, motor, and eyes (SEM) and face, legs, activity, cry, and consolability (FLACC) scores were recorded during the procedure, along with pulse rate and oxygen saturation, to measure pain during the procedure. This was followed by a self-administered visual analog scale (VAS) to assess the discomfort felt by the child. A statistically significant reduction in pain was observed with the usage of the vibration system and TENS, as measured by the FLACC scale, compared to the conventional method group. Similarly, statistically significant differences in SEM scores were noted between the vibrational precooling system group and the conventional method group, as well as between the TENS group and the conventional method group, with the highest scores observed in the conventional method group. The children reported the highest comfort levels with the usage of the vibration system, as indicated by the self-administered VAS. However, no statistically significant difference was observed within any group. The new vibrational precooling system as well as TENS can be effectively used to alleviate the pain experienced during the administration of local anesthesia. Singh K, Jhingan P, Mathur S, et al. Intercomparison of Efficacy of Transcutaneous Electrical Nerve Stimulation and Precooling Vibration Device on Pain and Anxiety Management during Administration of Local Anesthesia Injection in 6-12-year-olds. Int J Clin Pediatr Dent 2024;17(3):297-302.

Effects of wind speed on performance of a novel forced-air ice slurry wet precooling system

Aiming at the problems of low humidity and high dry consumption in the present forced-air precooling room, the combination of the ice slurry wet cooling system with the forced-air precooling was proposed, and a novel forced-air ice slurry wet precooling test platform was designed and built. The purpose of this paper is to experimentally study the effects of wind speeds on the performance of ice slurry wet precooling system by taking tomatoes as precooling objects, including precooling rate, precooling uniformity, precooling energy consumption and weight loss ratio of tomatoes. Also, the results are compared with those of other similar studies such as traditional forced-air precooling system. The results show that with the increase of wind speed, the precooling rate increases, the required precooling time is shortened, and the temperature variation coefficient of tomatoes decreases first and then increased, that is, the precooling uniformity becomes better and then worse. When the wind speed is 2.5 m/s, the overall precooling uniformity is the best. The precooling energy consumption decreases first and then increases, and is relatively low when the wind speed is between 1.5 m/s and 2.5 m/s (lowest at 2.5 m/s), which is lower than that of traditional forced-air system. With the increase of wind speed, the weight loss of tomatoes decreases first and then fluctuates slightly, and the weight loss ratio is about 0.1 %, which is much lower than that of tomatoes in the traditional forced-air precooling system. Overall, the maximum wind speed is not recommended to exceed 2.5 m/s for the precooling system studied in this work. The results can provide references for the further research and development of forced-air precooling technology.

Energetic assessment on a dual-temperature evaporation refrigeration system for hydrogen pre-cooling

The rapid, safe, and adequate refueling for hydrogen-based fuel cell vehicles relies on deep pre-cooling on the station side, which brings significant energy consumption. Step cooling is an ideal solution for the occasion with a large temperature drop. In this paper, a novel pre-cooling system is proposed by incorporating two-temperature evaporation to realize step cooling in the hydrogen refueling station. The pre-cooling load, system performance, and energy-saving potential are investigated under variable storage configurations and working conditions. The results show that the integral pre-cooling load increases linearly with the ambient temperature. However, the load share and the system performance are affected by the hydrogen intermediate temperature, the optimal value of which exhibits a nearly linear relationship with the ambient temperature. The novel system can save up to 30.2 % electricity relative to the conventional system with a single evaporator.

Design and optimization of liquid nitrogen precooling BOG re-liquefaction process for LNG ships

BOG re-liquefaction process is a necessary part for the safety of LNG cargo ships, and it is also the most common way to deal with evaporated gas (BOG) in LNG ships. Therefore, how to optimize the re-liquefaction process and save energy consumption is a problem that cannot be ignored in BOG re-liquefaction system. In this paper, based on the traditional BOG re-liquefaction process, a liquid nitrogen precooling circulation system is added and linked with the nitrogen purging system. Aspen HYSYS software was used to simulate and analyze the exergy efficiency, specific power consumption, exergy efficiency in the proposed liquefaction process. In addition, we introduced a bacterial foraging algorithm to optimize the process parameters. According to the operation results, the optimized process has a specific power consumption of 1.028 kWh/kgLNG, which is 21.53 % lower than that of the original NH3 and CO2 precooling system. Changing the traditional precooling system to liquid nitrogen tank reduces the complexity of the liquefaction system and improves the reliability of the system. Because liquid nitrogen has excellent cryogenic energy, small size, cheap price, safety in the actual use process and the linkage with the purge device on board, it shows excellent performance in the process of BOG pre-cooling liquefaction.

Performance Evaluation of Cryogenic Liquefaction System Precooled by Combined Vapour Compression-Absorption Refrigeration System

Liquefaction is a high-energy-consuming process. One of the most efficient methods of lowering energy consumption use is to run a precooled cycle with a cascade refrigeration system. When compared with the vapour compression system, the merit of adopting a cascade system is that it consumes very less energy. Another advantage is that non-traditional energy sources such as geothermal and solar might be used to power these cycles. This paper examines a precooled Linde Hampson-liquefaction system using a double-stage cascade vapour compression-absorption refrigeration cycle that consists of an absorption system at the high-temperature stage and a compression system at the low-temperature stage to generate cooling at a small temperatures by using various refrigerants in the absorption and compression sections. The system's performance was evaluated by employing various combinations of natural refrigerants in the absorption section. Liquefaction of Nitrogen is carried out using a precooled Linde Hampson system and precooled liquefaction using a cascade refrigeration cycle. Nitrogen was liquefied using two methods in the current study. A thorough examination of the precooled system was conducted, and it was discovered that by employing a cascade refrigeration cycle, the input required per unit mass of gas liquefied is decreased. The performance metrics of the liquefaction system, such as Figure of Merit (FOM) and Liquid Yield, were discovered for both scenarios, and it is concluded that the usage of a cascade refrigeration system has more efficiency and consumes less energy than a system without an absorption chiller. The use of a precooled Linde Hampson system with cascade cycles improved liquefaction characteristics by 5-7%.

Study of an integrated vortex tube used in hydrogen pre-cooling system

In hydrogen refueling stations, a hydrogen pre-cooling system is essential to protect the onboard hydrogen storage cylinder from high-temperature damage during refueling. To address the high power consumption of existing systems, this study proposes an integrated vortex tube hydrogen pre-cooling system. This system combines the vortex tube with a two-stage compression refrigeration cycle to create a new refrigeration device. The vortex tube component is numerically simulated using the standard k-ε turbulence model. Comparative analysis of power consumption and coefficient of performance (COP) is conducted between the new system, single-stage, and two-stage hydrogen pre-cooling systems. The results indicate that the vortex tube, as the pressure ratio increases from 1.5 to 20, reduces power consumption by 26.37%–41.52% compared to the single-stage system. Additionally, it improves the COP by 30.9%–53.8% compared to the single-stage system. Furthermore, compared to the two-stage system, the vortex tube achieves power savings of 4.08%–10.44% and COP improvements of 4.3%–11.7%.

Effect of dispersant on the performances of an ice slurry-wet precooling system

This study addresses the problem of prolonged precooling time and excessive weight loss of fruits and vegetables during postharvest processes. Ice slurry precooling system shows potential but faces challenges like low undercooling and ice blockage. Dispersants are introduced to optimize heat and moisture transfer as well as the flow characteristics of the ice slurry. This research investigates the effects of four dispersants on the performance of an ice slurry-based wet precooling system through experiments. Key parameters analyzed include temperature and humidity in the chamber, cooling rate, and weight loss rate of the tested load. Results show that the addition of dispersants effectively reduces the freezing temperature, enhancing the cooling rate in the system. Among the four dispersants tested, sodium diacetate yields the lowest freezing temperature of −6.4 °C and the highest cooling rate of 0.3 °C min−1. Furthermore, dispersants influence moisture transfer between ice slurry and circulating air, impacting the humidity within the precooling chamber. Notably, the addition of sodium diacetate results in the lowest weight loss rate of 2.74 %. This research shows the potential of using dispersants in ice slurry-based wet precooling systems to enhance the postharvest preservation of fruits and vegetables.

극저온 냉동기를 활용한 기체 수소 예냉 시스템 검증에 관한 연구 Part II: CFD 시뮬레이션

극저온 냉동기를 활용한 기체 수소 예냉 시스템 검증에 관한 연구 Part II: CFD 시뮬레이션

An optimization of a pre-cooling system for batch processes: A case study of the tubular ice production process

Mathematical models for predicting the thermal behavior of feed water precooling systems for tubular ice makers were developed. A commercial water chiller and plate type heat exchanger were used as the cooling source and heat exchanging device. The simulation results suggest that the system, in which the feed water is circulated through the heat exchanger, provides a higher effectiveness (ε) with a lower heat capacity rate ratio of the feed water to the chilled water (wr) for a certain number of transfer units (NTU). In the range of the ice maker capacities popularly used, at a NTU of unity, the optimum heat capacity rate ratio of the feed water to the chilled water (wr) could be estimated to be 0.48. The water chillers would operate in the range of their minimum specific power consumptions when the feed water temperature was higher than 11 °C. The system has the potential to reduce the energy consumption about 6.7–11.6%. In addition, it can improve the productivity. The system was tested with a conventional ice maker. The energy consumption can be reduced as predicted by the model. The results could be also applied to a precooling or preheating of any production process.

Development of Energy-Saving Battery Pre-Cooling System for Electric Vehicles

The performance, lifetime, and safety of electric vehicle batteries are strongly dependent on their temperature. Consequently, effective and energy-saving battery cooling systems are required. This study proposes a secondary-loop liquid pre-cooling system which extracts heat energy from the battery and uses a fin-and-tube heat exchanger to dissipate this energy to the ambient surroundings. The liquid then passes through a chiller to complete the cooling loop. The air-conditioning system is also used to cool the battery only if the temperature of the cooling water exceeds the maximum permissible temperature. The cooling load of the air-conditioning system is thus greatly reduced. The feasibility of the proposed cooling system is demonstrated experimentally under four simulated seasonal environmental conditions, namely high summer (35 °C), mean summer (30 °C), spring and fall (20 °C), and winter (7 °C). The results show that the pre-cooling system can dissipate 1000 W of battery heat in high summer, 2000 W in low summer, 3167 W in spring and fall, and more than 4000 W in winter. In other words, the pre-cooling system greatly reduces the cooling load of the air-conditioning system, and hence significantly reduces its energy consumption.

극저온 냉동기를 활용한 기체수소 예냉 시스템의 검증에 관한 연구 Part I: 실험적 연구 및 이론적 분석

극저온 냉동기를 활용한 기체수소 예냉 시스템의 검증에 관한 연구 Part I: 실험적 연구 및 이론적 분석

Modeling and performance analysis of a pre-cooling and power generation system based on the supercritical CO2 Brayton cycle on turbine-based combined cycle engines

Turbine-based combined cycle (TBCC) engines are a promising system of hypersonic vehicles, the main problem being the thrust gap during propulsion. To solve this problem, we proposed a pre-cooling system of turbofan based on the supercritical carbon dioxide (sCO2) Brayton cycle for TBCC engines fueled by hydrocarbon. A pre-cooler was set in the intake of the turbofan engine to achieve coupling between the Brayton cycle and the turbofan engine. The turbofan and Brayton cycle models were established, and several weight and limited cold source parameters were used to evaluate the system's performance. The effects of the inlet air temperature drop and pressure drop caused by the pre-cooler on the engine performance were obtained. The relationship between thermal performance and system weight of the sCO2 Brayton cycle under different pre-cooling target temperatures and recuperated heat loads was also analyzed. The results showed that it is feasible to use sCO2 to pre-cool the inlet air and generate power. When the pre-cooling target was set to Ma 2.2, the simple cycle could output 347 kW power with a power-to-weight ratio of 0.39 kW/kg. This study provides a new scheme for the pre-cooling and power generation technology of hydrocarbon-fueled TBCC engines.

Performance of an adiabatic pre-cooling system for concentrating solar power plants in arid areas

An adiabatic pre-cooling (AP) mechanical draft system for concentrating solar power (CSP) plants in arid regions is investigated. The cooling system amalgamates advantages of both dry and adiabatic cooling into a single system. We aim to demonstrate the system’s potentially advantageous spray water consumption characteristics and cooling performance, as it compares to conventional dry and wet-cooling, for arid-area CSP plants. This is done by investigating the AP system’s performance in isolation, via simulation and experimental validation, and a case study simulating performance of a 100 MW arid-area CSP plant with AP, dry and wet-cooling. Our primary contributions entail: analysing AP, dry and wet-cooling and CSP performance with hourly temporal resolution, from which annual hourly statistical summaries are presented, and quantifying AP and CSP performance in response to AP target saturation levels. Our performance assessment ambit includes: power cycle thermal efficiency, cooling or spray water consumption, gross output, parasitic consumption, plant capacity factor and intensive capital expenditure. Our main results show that: increased AP saturation beyond ≈80 % yields insignificant power cycle thermal efficiency enhancement, with gross output stabilising at >70 % saturation. Nonetheless, at 99 % saturation, AP boosts power cycle thermal efficiency by 1.61 % above dry-cooling, consumes 14.61 % less water than wet-cooling, and can increase power block capital cost by 14.19 % before the plant’s intensive capital expenditure equals that with dry-cooling. Furthermore, a 10 percentage point increase in AP saturation level increases the intensive cooling water consumption by ≈26.75 % on average, reduces the cooling parasitic energy consumption by ≈5.37 % on average, and raises the plant capacity factor by ≈0.35 % on average.

Theoretical study on the wetting rate in wet channel of dew-point evaporative cooler based on Marangoni effect

Dew-point evaporative cooler is widely concerned as a fresh air precooling system, for its high efficiency, energy saving and environmental protection. A mathematical model for a plate-type counter flow dew-point evaporative cooler is developed in the paper, in which the film shrinkage induced by the Marangoni effect is taken in account. The results show that the model based on Marangoni effect has a higher accuracy compared to the model with wetting rate σ = 100%, in which the Average Relative Deviation from the experiment decreases by 15.8%. The wettability distribution characteristics are investigated. Along the air flow, the transverse contraction distance of film is varied, which mostly depends on the evaporation process. The higher inlet air temperature, the lower inlet air humidity, the higher velocity of inlet air, the larger channel gap, and the higher ratio of working air to inlet air would cause the higher Marangoni number and lower wetting rate. Further, a constant value of wetting rate 96.2% is recommended to simplify the calculation, while the Average Relative Deviation of the simulated results compared to the actual process is only 0.47%.