Mechanical Compressor Research Articles

Performance analysis of activated carbon + HFC-134a adsorption coolers

The purpose of this paper is to present the results of performance analysis of a heat driven continuous vapor adsorption refrigerator with activated carbon as the adsorbent and 1,1,1,2-tetrafluoroethane (HFC-134a) as the refrigerant. A set of four adsorption cells takes on the role of the mechanical compressor in the conventional vapor compression refrigeration (VCR) system. Three specimens of activated charcoal under various packing densities were investigated. A parametric analysis was carried out with several evaporating, condensing/adsorbing and desorbing temperatures which are typical operating conditions catered to by HFC-134a. A new integrated relative performance evaluation scheme is proposed. It uses the maximum cycle uptake difference as a factor against which the coefficient of performance (COP) and exergetic efficiency are evaluated. It is shown that there is an optimal set of operating conditions wherein the exergetic efficiency is the maximum. A major part of the thermal energy input is for sensible heating of the compressor body.

Experimental results on V-M type pulse tube refrigerator

This article mainly introduces experimental results on a new type pulse tube refrigerator named as V-M type pulse tube refrigerator. The main difference from Stirling type or G-M type pulse tube refrigerator is that thermal compressor similar to that of a V-M cryocooler is used instead of mechanical compressor. By using temperature difference between room temperature and liquid nitrogen, pressure wave with high to low pressure ratio around 1.2 is obtained. This pressure wave is used to generate cooling effect at the cold end. With a 20 K pre-cooler, this machine reaches lowest temperature 5.25 K by using helium 4 at 0.77 Hz, 19 bar charge pressure. DC flow plays an important role in our system. It not only influences the final obtainable lowest temperature, but also is used to increase cold end cool-down speed. Total volume of the V-M type pulse tube refrigerator is around 3.3 l. However, dead volume inside rotor housing occupies about 2.8 l and can be much reduced.

GAS COMPRESSION USING TEMPERATURE SWING ADSORPTION

For a manned mission to Mars, NASA is interested in providing pure carbon dioxide at close to 1 bar to react with hydrogen to form methane and water. The Martian atmosphere is approximately 95% carbon dioxide, 2.7% nitrogen, 1.6% argon, and 0.7% other compounds at a pressure of about 0.008 bar. If the carbon dioxide is adsorbed at a low temperature and then the system is closed and heated, the pressure will increase because of both desorption and expansion of the gas. Usually the pressure increase due to desorption will be significantly larger than the gas expansion. By operating adsorption systems in series, significantly higher pressures can be obtained. Several systems were designed at a conceptual level for use on Mars as reliable alternatives to a mechanical compressor. Solar energy will be used for heating. Methods to remove most of the impurities during the compression process are explored.

The compression of hydrogen in an electrochemical cell based on a PE fuel cell design

The compression of gases in conventional compressors is often combined with low efficiency and the contamination of the compressed gases. In this paper, a system is described that uses an electrochemical cell for the compression of hydrogen. This electrochemical hydrogen compressor operates at lower hydrogen flux than mechanical hydrogen compressors. Further development of polymer electrolyte membrane (PEM) fuel cells afford a good prospect of realizing the electrochemical compression on a competitive basis. A specialized gas diffusion layer established the possibility to pressurize the cathode volume up to 54 bar. The ohmic resistance and pressure stability have been rescued by an improved membrane electrode assembly (MEA). A three cell stack on a laboratory scale has been designed. Data of single cell and stack experiments will be discussed in this paper. The advantages of the electrochemical system, apart from the efficiency, are: noiseless operation, purified hydrogen and simplicity of the system cooling.

A combined-cycle refrigeration system using ejector-cooling cycle as the bottom cycle

A combined-cycle refrigeration system (CCRS) that comprises a conventional refrigeration and air-conditioning system using mechanical compressor (RAC/MC) and an ejector-cooling cycle (EJC) is proposed and studied. The EJC is driven by the waste heat from the RAC/MC and acts as the bottom cycle of the RAC/MC. A system analysis shows that the COP of a CCRS is significantly higher than a single-stage refrigeration system. Improvement in COP can be as high as 18.4% for evaporating temperature of the RAC/MC Te at −5°C. A prototype of the CCRS was built and tested in the present study. Experimental results show that at Te=−4.5°C, COP is improved by 14% for a CCRS. For Te at 5°C, COP can be improved by 24% for a CCRS with higher condensing temperature of the RAC/MC. The present study shows that the CCRS using the ejector-cooling cycle as the bottom cycle of the RAC/MC is viable. Further improvement in COP is possible since the prototype is not designed and operated at an optimal condition.

D14 宇宙用熱駆動コンプレッサの基礎的動作特性の取得(熱音響エンジン)

A standing-wave-type thermal compressor can generate the pressure wave with the thermoacoustic effect. Because thit compressor without mechanical moving parts is driven only by the thermal input, reliability of a compressor system can be greatly enhanced. In this study, a tentative thermal compressor for 1-2W@60-80K pulse tube cryocoolers is designed and investigated with Argon gas of 1MPa. This thermal compressor consists of heat exchangers, a stack of SUS, a resonator tube of Max 7m and an attachable buffer tank. First, characteristics of a resonator are studied by using a mechanical linear compressor at various driving frequencies or displacement volumes. Next, the energy flow in the whole thermal compressor system is estimated and energy-conversion efficiencies are obtained.

C11 VM 型パルス管冷凍機の基本特性

Two different types of thermal compressors instead of the mechanical compressor were introduced for the low frequency pulse tube system. Simplified work flow analysis has been developed to find out the feasibility of the thermal compressor system. Result indicates the cold thermal compressor operating between 300 K and 40 K could be applied to 4 K pulse tube cooler effectively.

Energy efficient combined superheated steam dryer/MED

In a world of depleting fossil fuel resources, energy conscious research activities have become relevant for all industrial applications. Drying as an energy intensive process, is one example when conventional air drying is replaced by superheated steam (SHS) drying. This work presents a novel arrangement which reduces the SHS drying energy consumption. The analysis is applied to a milk powder producing plant that includes both concentration and drying processes. These are powered by a gas turbine of the simple Brayton cycle type. The raw feed is preheated before being concentrated in a single effect evaporator driven by a mechanical vapour compressor (MVC). The drying SHS in the dryer operates in a recycled mode while the evaporated water is purged and compressed in a two stage MVC equipped with an intercooler and aftercooler. The purged compressed steam is used to boost the SHS temperature from the circulating blower exit up to the required inlet temperature of the dryer. Use is made of the waste energy of the gas turbine exhaust. The balance of the recovered energy drives a multiple effect desalination (MED) unit to produce fresh water. The analysis coveres a range of dryer inlet temperatures of 150–275°C. The preheater surface area and feed concentrator shaft power per ton of powder (TP)/h are 30.4 m 2 and 34.5 kW, respectively. For the dryer, the ratio of SHS COP t/air COP t ranges from 2.51-1.94 for 150–275°C inlet temperature respectively. The overall power required/TP h is 502–423 kW, and the fresh water produced varied from 10.82–12.51 gallons/kWh for a 150–275°C inlet temperature respectively. The water produced can satisfy the requirements of about 40% of the milking heads.

Simulation Of Integrated Systems Of Evaporation Plants And Different Energy Conservation Techniques

This paper describes the flowsheeting program EVAPSYS, developed for both design and evaluation calculations of any type of evaporation plants. The evaporation plant may be simulated either separately or integrated with an energy conservation unit such as a mechanical compressor, a steam ejector, or an absorption heat cycle. Different component modules are incorporated to provide the user with maximum flexibility in constructing any evaporation plant. These modules include an evaporator, heat exchanger, expansion vessel, mixer, splitter, mechanical compressor, and steam ejector. Other component modules are incorporated to enable the user to simulate single-stage absorption cycles. This arrangement allows the program to be executed in three different modes: evaporation plants, absorption heat cycles, and heat-pump-driven evaporation systems. Three subfunctions are incorporated for computing the overall heat transfer coefficients for falling-film evaporators, forced circulation heat exchangers and evaporators, and black liquor in vertical tube evaporators. The physical and thermodynamic properties of different liquors for evaporation applications and different working fluid pairs for absorption heat cycle applications are available in the database of the program. Three examples from the desalination, sugar, and pulp and paper industries are given to demonstrate the program capabilities in simulating complex flowsheets of evaporation systems.

Treatment of saline wastewater for zero discharge at the Debiensko coal mines in Poland

The drainage water from mines in Poland has a daily contribution of, in the order of magnitude, 6,500 tons of chlorides and 0.5 ton of sulphates to the rivers Vistula (Wisla) and Oder (Odra). The largest amounts of these salts, about 78%, derive from 18 mines located mainly in the Katowice mine district. The high salt content in the water from the Vistula prevents at present its use in agriculture and causes tremendous economic losses due to corrosion attacks on pipes, machines, etc., within the industry. At present only about 4% of the river water can be classified as drinking water. To combat this problem a desalination project in Katowice has now almost been completed, including advanced treatment of wastewater for zero discharge from the two adjacent coal mines, Debiensko and Budryk. It implies elimination of 310 tons/d of salt discharge to the Odra River. The complete treatment processes are divided into three main sections: (1) pretreatment before reverse osmosis (RO) of about 12,400 m 3/d drainage water from the two mines with a salinity of around 16,000 mg/l TDS on the average; (2) RO plant including post-treatment of the RO permeate; (3) a thermal plant for concentration of brine (about 4,600 m 3/d) and separation of sodium chloride (NaCl) by crystallization, centrifuging and drying. The RO pretreatment includes algicide dosing in a storage tank, disinfection, flocculation/sedimentation and dual media filtration as well as granular activated carbon filtration. After a two-stage microfilter system (50 μ and 5 μ, respectively), the pretreated water is desalinated at 6–7 MPa in a RO system with spiral wound RO membranes. The RO permeate is decarbonated in a part-flow followed by addition of chemicals for disinfection and increase of the temporary hardness before distribution in the drinking water net. The flow into the thermal plant consists of the RO reject (about 2,700 m 3/d) with a salinity of around 80 g/l TDS and the brine flow (about 1,870 m 3/d) from the Budryk mine with about the same salinity. The first section of the thermal plant is composed of two brine concentrators, designed by Resources Conservation Company (RCC), USA. By using the seed crystal recycling technique it is possible to concentrate the feed to near the precipitation point for NaCl. The second section of the thermal plant includes one crystallizer for production of NaCl, two pusher centrifuges for salt removal from supersaturated brine and one fluidized bed dryer. The crystallizer is a forced circulation submerged-tube evaporator equipped with a mechanical vapor compressor. An additional section is also planned to be constructed for treatment of the purge from the crystallizer in order to recover other valuable chemical products and distillate. The process is fully automatic and controlled by programmable logic controllers. The plant has finally been designed by Energotechnika, Poland, after preparation of technical and economical planning of the project in coordination with Nordcap Ltd., RCC and VBB Viak-SWECO, Stockholm. In the summer 1994 the thermal plant was started up, and the RO plant is expected to be in operation during the spring 1995. The paper covers the project design with illustrations of the main parts of the plant and summarizes the results of the initial operation.

Cold Generation Systems: A Theoretical Approach

The objective of this study was to derive the thermodynamic formulae for ideal combined driving and cooling cycles when the objective of the overall cycle is to produce cooling by using a high-temperature heat source. For this it has been necessary to investigate absorption cooling thermodynamics and to focus on the analysis of one-, two- and three-stage cycles and multi-stage cycles in general. This paper has investigated the absorption thermodynamic principles involved to obtain simple formulae, in a similar way to the Carnot cycle. The first driving cycle considered has a high-temperature source such as a combustion process. From this driving cycle the heat dissipated at the lower temperature is used to drive the next consecutive driving and/or absorption cooling cycles. All the work produced in the driving cycles is used for the cooling cycles with mechanical compressors, whereas the dissipated heat of the last driving cycle is used to drive the absorption cycles. A simple universal law for driving and cooling cycles has been derived, which is applicable to combined heat and power (cogeneration) systems.

Rotary heat pump driven by natural gas

This paper describes the development of an efficient cycle based upon the rotation of a hybrid absorption/recompression arrangement. This novel refrigeneration cycle combines a mechanical compressor and absorption system, together with process intensification which exploits radial flow driven by centrifugal force. The system is driven by a gas-engine, in order to utilise the waste heat produced by the engine. The developed cycle avoids the use of CFCs (chlorofluorocarbons). Performance calculations are reported for a cycle using water and lithium bromide (H 2O/LiBr) and water sodium hydroxide-potassium hydroxide-caesium hydroxide (H 2O/NaOHKOHCsOH) as the working fluid. For each of the combinations, the refrigerant is water. This paper also discusses various cycles using different configurations in order to assess their feasibility.

Thermal modelling and energy conservation studies on freon rankine cycle cooling system with regenerative heat exchanger

This communication presents a thermodynamic analysis and assessment of a Freon fluid Rankine cycle cooling system. The system consists of two subsystems—Rankine engine (RE) power cycle and a vapour compression (V-C) refrigeration cycle. The heat engine subsystem consists of a boiler, turbine, condenser and a feed pump while the cooling subsystem consists of a mechanical compressor, condenser, evaporator and an expansion valve. A number of working fluid combinations for the RE cycle and V-C cycle subsystems have been chosen on the basis of their thermodynamic properties and their suitability judged in terms of the performance parameters, namely, the thermal efficiency of the power cycle and the coefficient of performance (COP) of the refrigeration cycle. A regenerative heat exchanger (RHE) is incorporated in the RE cycle to improve the cycle efficiency and achieve energy conservation. The effects of various operation parameters, namely, component temperatures, adiabatic expansion/compression efficiencies and effectiveness of the RHE on the overall COP have been assessed. It is found that R114 + R22 give the best overall system performance and the presence of the RHE improves the system COP significantly. The effect of V-C cycle condenser temperature is more pronounced as compared to that of the RE cycle condenser and similarly the effect of evaporator temperature in the V-C cycle is more pronounced as compared to that of the boiler in the Rankine cycle subsystem.

Industrial prototype of a hydrogen compressor based on metallic hydride technology

Abstract This work reports an improvement in the technique of metal hydride utilization in the hydrogen compression process: an industrial prototype of a thermochemical hydrogen compressor. This prototype uses a fixed bed (the reactor) of FeTi metallic alloy which reacts exothermically with hydrogen (absorption of the gas) at room temperature and at 1 MPa of pressure, and desorbs the pressurized hydrogen at one specific temperature for each pressure (250°C for 10 MPa). The project, manufacture, operation, performance and a comparison with a conventional mechanical compressor working in the compression of ultrapure hydrogen is presented. The cost of the prototype in Brazil is also given.

Analysis of a hybrid compression—absorption cycle using lithium bromide and water as the working fluid

Hybrid refrigeration cycles which combine a mechanical compressor and an absorption cycle in such a way that they share a single evaporator were analysed. The motivation for the investigation of hybrid cycles was the need to more efficiently utilize the output of an internal combustion engine. The hybrid cycles make efficient use of both the work and the heat output of an engine. Performance calculations are reported for a promising cycle which utilizes LiBr-H 2O as the working fluid. For this working fluid, the refrigerant is water. Owing to the potential sensitivity of the absorption cycle components to oil contamination, the cycle was analysed assuming an oil-free steam compressor (screw design). Although oil-free steam compressors are available, they are used only sparingly in the industry. The capital cost for such a compressor is very high and the isentropic efficiency of the available units is low. This combination of high cost and low performance results in poor economics for the hybrid cycle based on the available technology. However, the cycle has significant potential from a thermodynamic viewpoint and it provides an incentive for compressor manufacturers to refine the oil-free steam compression technology.

Tritium processing at the Savannah River Site: Present and future

Tritium handling equipment and methods at the Savannah River Site Tritium Facilities have been continually improved since tritium processing operations began in 1955. Several new technologies were introduced into the Tritium Facilities in the 1980’s. One of these is the use of fluidless, mechanical pumps (Normetex and Metal Bellows) to replace mercury pumps. A second is the use of metal hydride technology to store, purify, isotopically separate, pump, and compress hydrogen isotopes. Metal hydrides, such as La–Ni–Al alloys and Pd loaded on kieselguhr, offer significant flexibility and size advantages compared with conventional tritium handling technology, such as gas tanks, thermal diffusion columns, and mechanical compressors. Metal hydrides have been used in the Tritium Facilities since 1984 with the most important application of this technology being planned for the Replacement Tritium Facility, a $140 million facility scheduled for completion in 1990 and startup in 1991.

Application of mechanical compressors in schemes of evaporating units

Application of mechanical compressors in schemes of evaporating units

Microphone triggering circuit for elimination of mechanically induced frequency-jitter in diode laser spectrometers: implications for quantitative analysis

An electronic timing circuit using a microphone triggering device has been developed for elimination of mechanically induced frequency-jitter in diode laser spectrometers employing closed-cycle refrigerators. Mechanical compressor piston shocks are detected by the microphone and actuate an electronic circuit which ultimately interrupts data acquisition until the mechanical vibrations are completely quenched. In this way, laser sweeps contaminated by compressor frequency-jitter are not co-averaged. Employing this circuit, measured linewidths were in better agreement with that calculated. The importance of eliminating this mechanically induced frequency-jitter when carrying out quantitative diode laser measurements is further discussed.

Low‐pressure airlift fermenter for single cell protein production: I. Design and oxygen transfer studies

The energy consumption of a fermenter constitutes a major part of the operating expense of a single cell protein process. A low-pressure airlift fermenter was designed to reduce this cost. In this new design, the fermenter broth is kept below 120 cm in depth, and air alone is employed to fulfill the need of supplying oxygen, and cooling and agitating the broth. The use of low-pressure air from air blowers instead of air compressors lowers the capital cost of air delivery and reduces the energy consumption in the fermenter section to below 1 kWh/kg protein, a saving of over 70% as compared to a conventional stirred tank fermenter. It also eliminates the investment of mechanical agitators, heat exchangers, and air compressors. Sulfite oxidation studies confirmed the design concepts.

Comparison of open-chest cardiac massage techniques in dogs

Manual compression of the heart during open-chest cardiac massage (OCPR) has been shown to be superior to closed-chest compression. Our study sought to determine, in a canine model, the optimal hand position for manual compression of the heart. Twelve dogs were anesthetized with ketamine, an orotracheal tube was placed, and anesthesia was maintained with halothane and nitrous oxide. Cannulae were placed to monitor diastolic (DBP) and systolic (SBP) blood pressures, intracranial pressure (ICP), and common carotid blood flow (CCBF). Control values were obtained under light general anesthesia, and ventricular fibrillation was induced. External CPR (ECPR) was performed with a mechanical compressor before opening the chest and pericardium through the left fifth interspace. The following sequence of three hand positions was used for OCPR: technique A, one-handed technique with thumb on left ventricle, fingers over the right ventricle, and apex in palm; technique B, two-handed technique with right ventricle cupped in left hand and fingers of right hand over left ventricle; and technique C, one-handed technique with fingers of right hand over left ventricle and heart against sternum. Each was done at a rate of 60 compressions per minute with the operator blind to results during performance. All three techniques produced significantly (P less than .05) greater DBPs and CCBFs when compared with ECPR. All three also produced significantly lower (P less than .05) ICPs when compared with ECPR. DBPs, SBPs, CCBFs, and cerebral perfusion pressures were similar for techniques B and C, and all were significantly greater (P less than .05) than those achieved with technique A.(ABSTRACT TRUNCATED AT 250 WORDS)