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Selected issues of the multistage evaporator thermodynamics

100%
Cyklis P.
Czasopismo Techniczne
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-
PL
The well known multi-stage evaporation is an energy efficient process applied for concentrate juice production. There are however, some important issues concerning its thermodynamics which are not commonly revealed by the producers. The multi-stage design requires a properly designed control system to achieve maximum efficiency and capacity of the evaporator. In this paper, results of the author’s practical experience concerning the thermodynamics of the operation of the multi-stage evaporator in the industrial environment are presented. The report describes problems concerning the steady-state evaporator operation, choice of control parameters, and thermodynamics of the transient states.
2
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The role of the CFD modelling in the shape optimization of the pressure pulsations dampers

63%
Cyklis P., Młynarczyk P.
Czasopismo Techniczne
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-
PL
Pressure pulsations in volumetric compressors systems have an important influence on the compression power and reliability. This problem occurs not only in huge compressor systems, as in the natural gas piping, in gas mines or national transport systems, but also in a small refrigeration compressors in domestic applications. Nowadays, it is necessary to develop pressure pulsation damping elements which will be effective for different mass flow rate values. One of the solutions are passive damping elements in the form of various types of nozzles. In addition to the decrease of pressure pulsations value, the result is also an increase in power consumption of the compression. Therefore, shape optimization is necessary. In the article the possibility of optimizing the shape of such elements using computational simulations is discussed.
3
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Computer driven automatic control of the hybrid two stage refrigeration cycle

63%
Cyklis P., Duda R.
Czasopismo Techniczne
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-
PL
In the paper the method of automatic control of the two stage hybrid sorption-compression refrigeration system for different ambient conditions is presented. The main advantages of the system are its environmental friendly working fluids and waste or renewable low temperature heat source utilization. The control algorithm is designed for operation in four seasons’ conditions. During cold seasons the heat from the second stage condenser, as waste heat, may be used to increase the temperature of the heat pump source. The system is composed of dependent subsystems with individual controls, however it is controlled by the computer program as master control. The issues related to the optimization of operation of the refrigeration system, taking into account the maximum usage of available renewable or waste heat sources, are discussed in the paper.
4
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Nozzle suppressed pulsating flow CFD simulation issues

63%
Cyklis P., Młynarczyk P.
Czasopismo Techniczne
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-
PL
Pressure pulsations in volumetric compressor manifolds are one of the most important problems in compressor operation. These problems occur not only in huge compressor systems such as those used in natural gas piping in gas mines or national transport systems, but also in small refrigeration compressors found in domestic applications. Nowadays, systems require a new approach since in all applications, variable revolution speed compressors are introduced. Mufflers designed in a conventional way on the basis of the Helmholtz theory only have good pressure pulsation damping action within the designed frequency range. In the case of revolution speed change, the reaction of the damper designed according to the Helmholtz theory may be insufficient. Therefore, any innovative ideas for pressure attenuation is welcomed by the compressor industry. One of the possibilities to attenuate pressure pulsations over a wide range of frequencies is the introduction of specially shaped nozzles in the gas duct flow directly after the compressor outlet chamber. It is obvious that the nozzle attenuates pressure and flow pulsations due to energy dissipation, but at the same time, it also raises the requirement for the pumping power of the compressor. The estimation of nozzle pulsation attenuation may be assessed using CFD simulation. In the paper, the influence of the time step and viscous models choices have been shown. The differences between viscous and inviscid gas models have been shown.
5
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The hybrid sorption-compression refrigeration cycle control system

63%
Cyklis P., Duda R.
Czasopismo Techniczne
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-
PL
The requirements for environmentally friendly refrigerants promote the application of both CO2 and water as working fluids. Both solutions have disadvantages resulting from the high temperature limit for CO2 and the low temperature limit for water. This can be avoided by the application of the hybrid adsorption-compression system, where water is the working fluid in the adsorption cycle which is used to cool down the CO2 compression cycle condenser. The adsorption process is powered with a low-temperature renewable heat source such as solar collectors or waste heat sources. This solution has been developed by the authors of this paper and has not been reported in any other literature source. The different ambient conditions over the course of the year require specially designed controlprocedures and the automation system. The algorithm has to control positive and negative heat sources operation, valve actions, pumps, fans and compressor operation. In the control algorithm, the ambient temperature and solar conditions or other waste heat sources have to be introduced as control parameters, optimised to achieve maximum efficiency of the whole system. The refrigeration effect as a parameter has to be considered both for the refrigeration capacity as well as the CO2 evaporation temperature.
6
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An innovative ecological hybrid refrigeration cycle for high power refrigeration facility

63%
Cyklis P., Janisz K.
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vol. 36
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issue 3
321-330
EN
Searching for new refrigerants is one of the most significant scientific problems in refrigeration. There are ecological refrigerants commonly known: H2O and CO2. H2O and CO2 known as natural refrigerants, but they have problems:a high freezing point of H2O and a low triple point of CO2. These problems can be solved by the application of a hybrid sorption-compression refrigeration cycle. The cycle combines the application possibility of H2O in the high temperature sorption stage and the low temperature application of CO2 in the compression stage. This solution gives significant energy savings in comparison with the two-stage compressor cycle and with the one-stage transcritical CO2 cycle. Besides, the sorption cycle may be powered by low temperature waste heat or renewable heat. This is an original idea of the authors. In the paper an analysis of the possible extension of this solution for high capacity industrial refrigeration is presented. The estimated energy savings as well as TEWI (Total Equivalent Warming Impact) index for ecological gains are calculated.
7
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CFD Impulse Flow Simulation Through Shaped Nozzles

63%
Cyklis P., Młynarczyk P.
Czasopismo Techniczne
|
-
PL
Pressure pulsations in volumetric compressor manifolds are important issues in the compressor plant operation. For pressure pulsation attenuation, mufflers designed using the Helmholtz resonator approach are applied. Nowadays, the variable revolution speed compressors requires new design methods for pressure pulsation damping elements. One of the possibilities to attenuate the pressure pulsations is the introduction of specially shaped nozzles in the gas duct flow. In this paper, the impulse flow simulations conducted in FLUENT/ANSYS. The experimental validation of the simulation results is also presented.
8
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Content available

CFD Impulse Flow Simulation Through Shaped Nozzles

63%
Cyklis P., Młynarczyk P.
Czasopismo Techniczne
|
-
PL
Pressure pulsations in volumetric compressor manifolds are important issues in the compressor plant operation. For pressure pulsation attenuation, mufflers designed using the Helmholtz resonator approach are applied. Nowadays, the variable revolution speed compressors requires new design methods for pressure pulsation damping elements. One of the possibilities to attenuate the pressure pulsations is the introduction of specially shaped nozzles in the gas duct flow. In this paper, the impulse flow simulations conducted in FLUENT/ANSYS. The experimental validation of the simulation results is also presented.
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