Wyniki wyszukiwania - BazTech

1

Year-round operation the solar powered hybrid adsorption-compression refrigeration cycle

Cyklis Piotr, Duda Robert

Journal of Mechanical and Energy Engineering

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2019

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Vol. 3, No 4

317--322

EN

In our earlier papers a hybrid adsorption-compression refrigeration cycle was presented. The hybrid, two stages cycle is based only on the natural refrigerants: water and carbon dioxide. The main advantage of the hybrid cycle is that the carbon dioxide compression cycle is subcritical because during the year-round operation it is possible to maintain the condensing temperature below 20°C. During the hot season, this is achieved by adsorption cooling, during cold seasons the wet cooling tower is sufficient. Already several years of experience, allowed to gather a considerable amount of measurement data. The refrigeration system is working in our laboratory constantly since 2013. In 2015 the adsorption system was upgraded by the manufacturer. In 2017 frequency inverter for wet tower fan controlling was introduced. The refrigeration chamber was used for tests with different content and operation of the refrigeration chamber (loading and unloading). The assumed CO2 evaporating temperature was -35°C. The averaged for HT (High Temperature) part of the cascade (adsorption cycle only) COPHT=0.51 for the whole year 2018. This may be considered a very good performance. Averaged total COP for the cascade system: COP=0.9 compared to COP=0.84 for compression only refrigeration cascade, with much higher TEWI index. For comparison for two-stage compression (R407CHT+R744LT) cycle was used. This means that if the cooling tower fan operation is controlled using an inverter, adjusted to the actual heat removal demand, the hybrid cycle is not only ecological but also energetically efficient.

2

Transient model of heat pump cycle

Matysko R.

Journal of Mechanical and Energy Engineering

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2018

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Vol. 2, No 2

139--146

EN

This paper introduce a transient model of the propane heat pump cycle. The heat pump cycle model includes: a compressor model, a condenser model in lumped parameters, an evaporator model in lumped parameters, an expansion valve model, a heat source model (cooling chamber), a PID control system for heat recovery from superheated refrigerant vapour. The model allows estimate inertia of the heat pump cycle with the system of the heat recovery from superheated propane vapor. The presented theoretical model can determine unsteady and steady state conditions of the different subsystems in the heat pump cycle (condenser, evaporator, compressor). The article presents the results of calculations and determines the time of reaching steady states of the key systems of the heat pump system. The article also presents (in a graphical form) the behavior of the system where the setting was changed after reaching the steady state after 2000s from 50kW to 40kW at the thermal load of the additional heat recovery exchanger.

3

Energy efficiency improvement of the refrigeration cycle using an internal heat exchanger

Müller J.

Czasopismo Techniczne. Środowisko

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2016

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Y. 113, iss. 1-Ś

105--115

EN

A refrigeration cycle modified using an Internal Heat Exchanger is presented. For different refrigerants, the net effect of using an IHX is either positive or negative due to refrigerant properties and working conditions. Wet refrigerant vapor at the inlet of IHX improves the cycle in various aspects. The evaporator performance is much better when not superheating the vapor. A “pure” effect of subcooling the refrigerant liquid at the inlet of the expansion valve results in an increased specific heat of evaporation. For zeotropic mixtures, increased subcooling results in lowering the evaporating temperature without lowering the pressure in the evaporator. The EER value can be improved for some refrigerants and for specific working conditions. Theoretical and experimental evaluations of this concept are presented. Commonly used refrigerants were evaluated theoretically and tested in a 10 kW (cooling capacity) test rig. R22 and R407C were analyzed.

PL

W artykule przedstawiono obieg ziębniczy zmodyfikowany przez dodanie doziębiacza. Efekt końcowy zastosowania doziębiacza jest różny w zależności od użytych ziębników oraz warunków pracy. Wprowadzenie pary mokrej do doziębiacza skutkuje wieloma pozytywnymi efektami. Praca parowacza jest efektywniejsza, jeżeli nie służy on do przegrzewania pary ziębnika, doziębienie cieczy przed zaworem rozprężnym skutkuje zwiększeniem właściwego ciepła parowania. Dla mieszanin zeotropowych obserwuje się obniżenie temperatury parowania bez obniżania ciśnienia parowania. Zwiększenie wartości wskaźnika EER może być uzyskane przez odpowiedni dobór ziębników oraz parametrów pracy obiegu. Przedstawiono również wyniki badań eksperymentalnych dla powszechnie używanych ziębników na stanowisku o wydajności ziębniczej 10 kW.

4

Zastosowanie turbiny rozprężonej w ziębiarkowym obiegu sprężarkowym z CO2 jako czynnikiem chłodniczym

Kozioł J., Pach R.

Chłodnictwo : organ Naczelnej Organizacji Technicznej

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2016

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R. 51, nr 1-2

24--27

PL

Jednym ze sposobów ograniczenia strat dławienia w lewobieżnym obiegu sprężarkowym jest wykorzystanie turbiny rozprężnej. Efekt energetyczny uzyskiwany dzięki stosowaniu turbiny zależy od rodzaju czynnika obiegowego oraz od jego parametrów termicznych. Szczególnie korzystny efekt występuje w przypadku stosowania dwutlenku węgla (R744). W opracowaniu przedstawiono efekty zastosowania turbiny rozprężnej w obiegu lewobieżnym z R744 jako czynnikiem obiegowym. Dla przykładowego obiegu przedstawiono metodę oceny optymalnych parametrow temperatury (ciśnienia) czynnika obiegowego doprowadzanego do turbiny.

EN

One way to reduce throttling losses in compressor refrigeration cycle is to use the expansion turbine. The effect of energy obtained by the use of the turbine depends on the type of refrigerant used in the circulation. A particularly advantageous effect is obtained with the use of carbon dioxide (R744). The study shows an application variant of the expansion turbine. The example circuit presents a method to assess the optimal parameters -temperature (pressure) of circulating fluid supplied to the turbine.

5

Computer driven automatic control of the hybrid two stage refrigeration cycle

Cyklis P., Duda R.

Czasopismo Techniczne. Mechanika

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2015

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Y. 112, iss. 2-M

3--10

EN

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.

PL

W artykule przedstawiono metodykę automatycznego sterowania dwustopniowej adsorpcyjno-sprężarkowej kaskady chłodniczej w zależności od różnych warunków otoczenia. Główna zaleta prezentowanego systemu wynika z wykorzystania przyjaznych dla środowiska czynników chłodniczych. System wykorzystuje do pracy energię cieplną z niskotemperaturowych źródeł odnawialnych. Algorytm sterujący został przygotowany tak, aby utrzymać pracę systemu przez cały rok. Podczas okresu zimowego ciepło ze skraplacza, jako ciepło odpadowe, może zostać wykorzystane do podwyższenia temperatury źródła pompy ciepła. System zbudowany jest z zależnych od siebie podsystemów, dlatego ich praca zarządzana jest przez program komputerowy. Zostaną omówione zagadnienia związane z optymalizacją pracy systemu chłodniczego biorące pod uwagę maksymalne wykorzystanie dostępnych źródeł ciepła.

6

The influence of condensing pressures of the ethylene carrier cascade cycle on its refrigeration capacity

Nanowski D.

Journal of Polish CIMAC

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2014

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Vol. 9, no 3

67--72

EN

Ethylene, Propane and others liquefied gases as a cargo are transported at sea by temperature below 0°C. It requires sufficient efficiency of reliquefaction plant. Short description of that gas plant is shown including cascade system and its cooling processes are described. Based on Mollier diagrams the refrigeration capacity investigation of gas plant is done. This analysis is focused on condensing pressure which takes place in the condenser. Theoretical cycles are taken into account and real condensers of cargo compressor and screw compressor of refrigerant cycle are considered. Thermostatic expansion valves are employed in cascade cycles and their operation parameters are taken into account as well. Conclusions include some guidelines on condensing pressure and related operation parameters to maintain the gas plant with high efficiency of refrigeration capacity.

7

Dynamika odzysku ciepła w obiegu chłodniczym

Matysko R.

Chłodnictwo : organ Naczelnej Organizacji Technicznej

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2013

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R. 48, nr 3

6--9

PL

W pracy przedstawiono najprostszy możliwy dynamiczny model obiegu chłodniczego wraz z systemem sterowania. Model pozwala oszacować bezwładność instalacji chłodniczej, jak i pomp ciepła z systemem odzysku ciepła z pary przegrzanej. Do obliczeń przyjęto model skupiony. Model instalacji chłodniczej powiązany jest z modelem komory i obciążenia cieplnego o parametrach rozłożonych.

EN

Refrigeration devices except receiving low temperatures in cooling chambers or air conditionings systems enable to receive a high temperatures in heal pumps. Refrigeration cycle allows to obtain high temperature in the room from the heat transfer process in the condenser. Paper presents the simplest transient model of the ideal propane refrigeration cycle, with the system of the heat recovery from superheated vapor. Refrigeration cycle model includes: -condenser model in lumped parameters -evaporator model in lumped parameters -expansion valve model depends from condenser and evaporator parameters -compressor model -PID control system for heat recovery from superheated refrigerant vapour. Model allows to estimate the inertia of the refrigeration cycle.

8

Gas plant of ethelyne gas carried and a two stages compression optimization of ethylene as a cargo based on thermodynamic analysis

Nanowski D.

Journal of Polish CIMAC

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2012

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Vol. 7, no 1

183-190

EN

Ethylene as a cargo is more and more popular in maritime transport. Its temperature approx. -104°C during discharging requires sufficient efficiency of reliquefaction plant. Short description of that gas plant is shown including cascade system and processes are described. Based on Mollier diagram and ethylene mass flows, refrigeration capacity of the system is calculated when some changes in the cargo economizer are done. Some of these changes are carried out by crew members of gas carriers in order to reduce second stage discharge temperatures of reciprocating compressors. These losses of refrigeration efficiency are calculated to assess its influence on Ethylene temperature in the cargo tanks. On the other hand some assumptions are used to improve refrigeration capacity by Ethylene compression process.