Oxygen Liquefier Using a Mixed Gas Refrigeration Cycle

2003 ◽  
Author(s):  
Vijayaraghavan Chakravarthy ◽  
Joe Weber ◽  
Abdul-Aziz Rashad ◽  
Arun Acharya ◽  
Dante Bonaquist
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Low Cost ◽  
Rankine Cycle ◽  
Small Scale ◽  
Refrigeration Cycle ◽  
Mixed Gas ◽  
Unit Power ◽  
Design Selection ◽  
Pressure Swing

This paper presents the design, selection of equipment, testing, and analysis of a 2 TPD (76 kg/hr) prototype oxygen liquefier that employs a mixed gas refrigeration cycle. Small scale oxygen plants (30–60 TPD) based on VPSA systems (Vapor Pressure Swing Adsorption) periodically require liquid back-up to provide uninterrupted supply of O2 gas to customers during planned plant maintenance. Supply of liquid for back-up, especially to customers in remote locations, is expensive and difficult. Economically designed MGR liquefiers will fulfill this market need. The 2 TPD prototype O2 liquefier is based on the dual loop MGR Rankine cycle (see Figure 1). The forecooler loop provides refrigeration at the warm end (233K). R507 is used as a refrigerant for the forecooler in the warm end loop. The main refrigeration loop uses a mixture of R218, R14 and N2. The main advantage of separating the refrigerants into two different loops is to avoid freezing of high boiling point refrigerants at liquid O2 temperatures in the main refrigeration loop. The process and mixture composition were optimized using the HYSYS process simulation package. Very useful insights were gained in terms of reducing the irreversibilities in the heat exchanger. Low cost innovative designs were adopted for the heat exchangers. For example: (1) plate-and-frame heat exchangers were successfully used for multiple gas streams, (ii) a spirally wound coiled heat exchanger was used to liquefy oxygen. Similarly, the compressors used in the forecooler and main cycle were low cost, off-the-shelf items used in conventional refrigeration systems. The liquefier unit was initially demonstrated and a liquid making capacity of 1.5 TPD at a unit power of 44 kW/TPD was achieved. Subsequent modifications to the heat exchangers resulted in meeting the design expectations at a unit power of 37 kW/TPD.

1-D Model Analysis of Tesla Turbine for Small Scale Organic Rankine Cycle (ORC) System

2017 ◽  
Author(s):  
Jian Song ◽  
Chun-wei Gu
Keyword(s):  
Large Scale ◽  
Low Cost ◽  
Organic Rankine Cycle ◽  
Axial Flow ◽  
Rankine Cycle ◽  
Expansion Ratio ◽  
Working Fluid ◽  
Small Scale ◽  
Low Grade ◽  
D Model

Energy shortage and environmental deterioration are two crucial issues that the developing world has to face. In order to solve these problems, conversion of low grade energy is attracting broad attention. Among all of the existing technologies, Organic Rankine Cycle (ORC) has been proven to be one of the most effective methods for the utilization of low grade heat sources. Turbine is a key component in ORC system and it plays an important role in system performance. Traditional turbine expanders, the axial flow turbine and the radial inflow turbine are typically selected in large scale ORC systems. However, in small and micro scale systems, traditional turbine expanders are not suitable due to large flow loss and high rotation speed. In this case, Tesla turbine allows a low-cost and reliable design for the organic expander that could be an attractive option for small scale ORC systems. A 1-D model of Tesla turbine is presented in this paper, which mainly focuses on the flow characteristics and the momentum transfer. This study improves the 1-D model, taking the nozzle limit expansion ratio into consideration, which is related to the installation angle of the nozzle and the specific heat ratio of the working fluid. The improved model is used to analyze Tesla turbine performance and predict turbine efficiency. Thermodynamic analysis is conducted for a small scale ORC system. The simulation results reveal that the ORC system can generate a considerable net power output. Therefore, Tesla turbine can be regarded as a potential choice to be applied in small scale ORC systems.

Dynamic Simulation and Optimization of an Experimental Micro-CSP Power Plant

2015 ◽  
Author(s):  
Matthias Mitterhofer ◽  
Matthew Orosz
Keyword(s):  
Control Strategy ◽  
Low Cost ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Economic Benefits ◽  
Solar Thermal ◽  
Small Scale ◽  
Pinch Point ◽  
Simulation And Optimization ◽  
Dynamic Representation

Small scale solar thermal systems are increasingly investigated in the context of decentralized energy supply, due to favorable costs of thermal energy storage (TES) in comparison with battery storage for otherwise economical PV generation. The present study provides the computational framework and results of a one year simulation of a low-cost pilot 3kWel micro-Concentrated Solar Power (micro-CSP) plant with TES. The modeling approach is based on a dynamic representation of the solar thermal loop and a steady state model of the Organic Rankine Cycle (ORC), and is validated to experimental data from a test site (Eckerd College, St. Petersburg, Florida). The simulation results predict an annual net electricity generation of 4.08 MWh/a. Based on the simulation, optimization studies focusing on the Organic Rankine Cycle (ORC) converter of the system are presented, including a control strategy allowing for a variable pinch point in the condenser that offers an annual improvement of 14.0% in comparison to a constant condensation pinch point. Absolute electricity output is increased to 4.65 MWh/a. Improvements are due to better matching to expander performance and lower condenser fan power because of higher pinch points. A method, incorporating this control strategy, is developed to economically optimize the ORC components. The process allows for optimization of the ORC subsystem in an arbitrary environment, e.g. as part of a micro-grid to minimize Levelized electricity costs (LEC). The air-cooled condenser is identified as the driving component for the ORC optimization as its influence on overall costs and performance is of major significance. Application of the optimization process to various locations in Africa illustrates economic benefits of the system in comparison to diesel generation.

Design and Analysis of Thermoacoustic Refrigerators Using Air as Working Substance

2019 ◽  
Vol 27 (01) ◽  
pp. 1950008 ◽  
Author(s):  
B. G. Prashantha ◽  
S. Seetharamu ◽  
G. S. V. L. Narasimham ◽  
M. R. Praveen Kumar
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Low Cost ◽  
Design Strategies ◽  
Software Simulation ◽  
Design And Optimization ◽  
Theoretical Design ◽  
Resonator Design ◽  
Simulation Results ◽  
Thermoacoustic Refrigerators

In this paper, the design of 50 W thermoacoustic refrigerators operating with air as working substance at 10 bar pressure and 3% drive ratio for a temperature difference of 28 K is described. The design strategies discussed in this paper help in design and development of low cost thermoacoustic coolers compared to helium as the working substance. The design and optimization of spiral stack and heat exchangers, and the promising 0.2[Formula: see text] and 0.15[Formula: see text] resonator design with taper and divergent section with hemispherical end are discussed. The surface area, volume, length and power density of the hemispherical end design with air as working substance is found better compared to the published 10 and 50 W coolers using helium as the working substance. The theoretical design results are validated using DeltaEC software simulation results. The DeltaEC predicts 51.4% improvement in COP (1.273) at the cold heat exchanger temperature of [Formula: see text]C with air as working substance for the 50[Formula: see text]W 0.15[Formula: see text]TDH resonator design compared to the published 50[Formula: see text]W 0.25[Formula: see text]TDH resonator design with helium as working substance.

Novel Parabolic Trough Collectors Driving a Small-Scale Organic Rankine Cycle System

2007 ◽  
Author(s):  
P. Kohlenbach ◽  
S. McEvoy ◽  
W. Stein ◽  
A. Burton ◽  
K. Wong ◽  
...  
Keyword(s):  
Steel Substrate ◽  
Low Cost ◽  
Sheet Steel ◽  
Organic Rankine Cycle ◽  
Glass Tube ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Small Scale ◽  
Inlet Temperature ◽  
Parabolic Trough

This paper presents component performance results of a new parabolic trough collector array driving an organic Rankine cycle (ORC) power generation system. The system has been installed in the National Solar Energy Centre at CSIRO Energy Technology in Newcastle, NSW, Australia. It consists of four rows of 18 parabolic mirrors each in a 2×2 matrix with a total aperture area of approximately 132m2. The absorber tube is a laterally aligned, 40mm copper tube coated with a semi-selective paint and enclosed in a 50mm non-evacuated glass tube to reduce convection losses. The mirror modules, which are light-weight and robust, are made from thin low iron back silvered glass bonded to a sheet steel substrate. They are supported by a box truss on semi circular hoops running on rollers for single axis tracking. The mirror design has been chosen to allow low-cost manufacturing as well as simple commissioning and operation. The ORC unit is a FP6 unit sourced from Freepower Ltd. with a net power output of 6kWel at 180°C inlet temperature and a total heat input of 70 kWth. It uses a two-stage expansion process with hydrofluoroether as the working fluid. A wet cooling tower is used to dissipate the reject heat from the ORC. The two key components of the envisioned system are the trough reflector/receiver and the ORC unit. The optical performance of the mirror elements was investigated with regard to the flux mapping onto the receiver tube. The ORC unit has been tested separately using an electrical oil heater as the heat source. This paper presents results for irradiation capture and intensity over the receiver width of a single trough mirror module. The complete system including trough collectors and ORC has not been in transient operation yet, thus experimental steady-state results of the ORC unit are presented.

scholarly journals Modelling of Polymeric Shell and Tube Heat Exchangers for Low-Medium Temperature Geothermal Applications

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2737
Author(s):  
Francesca Ceglia ◽  
Adriano Macaluso ◽  
Elisa Marrasso ◽  
Maurizio Sasso ◽  
Laura Vanoli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Heat Transfer Area ◽  
Geothermal Fluid ◽  
Shell And Tube

Improvements in using geothermal sources can be attained through the installation of power plants taking advantage of low and medium enthalpy available in poorly exploited geothermal sites. Geothermal fluids at medium and low temperature could be considered to feed binary cycle power plants using organic fluids for electricity “production” or in cogeneration configuration. The improvement in the use of geothermal aquifers at low-medium enthalpy in small deep sites favours the reduction of drilling well costs, and in addition, it allows the exploitation of local resources in the energy districts. The heat exchanger evaporator enables the thermal heat exchange between the working fluid (which is commonly an organic fluid for an Organic Rankine Cycle) and the geothermal fluid (supplied by the aquifer). Thus, it has to be realised taking into account the thermodynamic proprieties and chemical composition of the geothermal field. The geothermal fluid is typically very aggressive, and it leads to the corrosion of steel traditionally used in the heat exchangers. This paper analyses the possibility of using plastic material in the constructions of the evaporator installed in an Organic Rankine Cycle plant in order to overcome the problems of corrosion and the increase of heat exchanger thermal resistance due to the fouling effect. A comparison among heat exchangers made of commonly used materials, such as carbon, steel, and titanium, with alternative polymeric materials has been carried out. This analysis has been built in a mathematical approach using the correlation referred to in the literature about heat transfer in single-phase and two-phase fluids in a tube and/or in the shell side. The outcomes provide the heat transfer area for the shell and tube heat exchanger with a fixed thermal power size. The results have demonstrated that the plastic evaporator shows an increase of 47.0% of the heat transfer area but an economic installation cost saving of 48.0% over the titanium evaporator.

scholarly journals Heat Transfer Enhancement by Using Different Types of Inserts

2014 ◽  
Vol 6 ◽  
pp. 250354 ◽  
Author(s):  
S. Tabatabaeikia ◽  
H. A. Mohammed ◽  
N. Nik-Ghazali ◽  
B. Shahizare
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Low Cost ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Thermal Systems ◽  
Twisted Tapes ◽  
High Efficient

Heat transfer enhancement has been always a significantly interesting topic in order to develop high efficient, low cost, light weight, and small heat exchangers. The energy cost and environmental issue are also encouraging researchers to achieve better performance than the existing designs. Two of the most effective ways to achieve higher heat transfer rate in heat exchangers are using different kinds of inserts and modifying the heat exchanger tubes. There are different kinds of inserts employed in the heat exchanger tubes such as helical/twisted tapes, coiled wires, ribs/fins/baffles, and winglets. This paper presents an overview about the early studies on the improvement of the performance of thermal systems by using different kinds of inserts. Louvered strip insert had better function in backward flow compared to forward one. Modifying the shape of twisted tapes led to a higher efficiency in most of the cases excpet for perforated twisted tape and notched twisted tape. Combination of various inserts and tube with artificial roughness provided promising results. In case of using various propeller types, heat transfer enhancement was dependent on higher number of blades and blade angle and lower pitch ratio.

Theoretical Analysis of Effects of Solution Heat Exchanger on the Performance of Mixed Absorption Refrigeration Cycle

2012 ◽  
Vol 170-173 ◽  
pp. 2521-2524
Author(s):  
Wen Li ◽  
Jun Hua Wan ◽  
Jing Liu ◽  
Zu Yi Zheng ◽  
Wen Ming Xu
Keyword(s):  
Heat Exchanger ◽  
Theoretical Analysis ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Solution Temperature ◽  
Refrigeration Cycle ◽  
Absorption Refrigeration ◽  
Cooling Water Flow Rate

The model of solution heat exchangers of mixed absorption refrigeration cycle was developed. The effects of strong solution temperature difference between inlet and outlet of solution heat exchanger on the coefficient of performance (COP) and cooling water flow rate of mixed absorption refrigeration cycle were analyzed, at the same time, the effects of temperature difference on the unit heat exchange area of counter-flow and cross-flow solution heat exchangers were analyzed. The theoretical analysis results showed that there was an optimal value for the strong solution temperature difference, for the mixed absorption system, the optimal temperature difference was about 12°C, the corresponding COP was 11.2% higher and the cooling water flow rate was 7.8% less than that of system without heat exchanger.

scholarly journals Assessment of Methods for Performance Comparison of Pure and Zeotropic Working Fluids for Organic Rankine Cycle Power Systems

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1783 ◽  
Author(s):  
Jesper Graa Andreasen ◽  
Martin Ryhl Kærn ◽  
Fredrik Haglind
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Power Systems ◽  
Temperature Difference ◽  
Power Output ◽  
Heat Exchangers ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluids ◽  
Net Power Output

In this paper, we present an assessment of methods for estimating and comparing the thermodynamic performance of working fluids for organic Rankine cycle power systems. The analysis focused on how the estimated net power outputs of zeotropic mixtures compared to pure fluids are affected by the method used for specifying the performance of the heat exchangers. Four different methods were included in the assessment, which assumed that the organic Rankine cycle systems were characterized by the same values of: (1) the minimum pinch point temperature difference of the heat exchangers; (2) the mean temperature difference of the heat exchangers; (3) the heat exchanger thermal capacity ( U ¯ A ); or (4) the heat exchanger surface area for all the considered working fluids. The second and third methods took into account the temperature difference throughout the heat transfer process, and provided the insight that the advantages of mixtures are more pronounced when large heat exchangers are economically feasible to use. The first method was incapable of this, and deemed to result in optimistic estimations of the benefits of using zeotropic mixtures, while the second and third method were deemed to result in conservative estimations. The fourth method provided the additional benefit of accounting for the degradation of heat transfer performance of zeotropic mixtures. In a net power output based performance ranking of 30 working fluids, the first method estimates that the increase in the net power output of zeotropic mixtures compared to their best pure fluid components is up to 13.6%. On the other hand, the third method estimates that the increase in net power output is only up to 2.56% for zeotropic mixtures compared to their best pure fluid components.

Sign in / Sign up

Export Citation Format

Share Document