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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Analysis of simultaneous cooling and heating in supermarket refrigeration systems

Marigny, Johan January 2011 (has links)
In this master thesis project, conventional supermarket refrigeration systems using R404A are compared with refrigeration system solutions using natural refrigerants such as carbon dioxide and ammonia. This systems analysis considers the behavior of those systems in floating condensing and heat recovery mode. System heating and cooling COP have been calculated by using computer simulation with the calculation software EES (Engineering Equation Solver). The impact of important parameters such as sub-cooling, external superheating and compressor discharge was also determined through the computer models.The estimation of the system annual energy consumptions shows that systems using natural refrigerant can compete with systems using artificial refrigerant by using heat recovery system such as heat pump cascade, heat pump cascade for sub-cooling, fixed pressure system and de-superheater. If the indirect emission of systems using natural refrigerant and artificial refrigerant is approximately similar, the direct emission for carbon dioxide systems and ammonia systems can be estimated to be 10000 times less important than R404A systems.Multi-unit refrigeration systems have also been studied in this project; it appears that in theory COP improvement of 10% is possible if the condensing temperature of each unit is controlled adequatelly. / B

The design and care of refrigerating apparatus

Holland, Archibald Dinsmore 08 1900 (has links)
No description available.

The design and development of a magnetic refrigerator

Mand, G. S. January 1987 (has links)
A new tvpe ot macnetic retricerator usine a rotatine belt eeometrv has been desiened and developed. The retricerator u.e. the maenetocaloric ettect. that is. the heat inc or cooline ot a maenetic material on application or removal ot a maen.tic tield. to execute a Carnot cvcle. An antiterromaanetic material. Gadolinium Gallium Garnet, Gd3Gas012 (GGG) , i. used ae the retricerant. This is in the torm ot a belt which run. throuch the bore ot a .uperconduct1na solenoid macnet to execute the cyole. The retricerator has been developed in three staces, Fir.tlv the belt ceometry was de.icned. oonstructed and te.ted. This lead to the development ot the model one retricerator. and ba.ed on the.e results the model two retriaerator was con.tructed. Re.ult •• trom the model two retricerator. show an anomalous temperature increa.e in the .ource recion resul tine trom a re - lIlaenetieation ot the belt. Purthermore. entrained tluid ettects limit the operatinc temperature span. However. the belt concept has been .ucce.etullv realised with it beina operated at trequencie. ot up to 30 rpm in macnetic tields not exceedine "T.

A theoretical and experimental investigation of an absorption refrigeration system for application with solar energy units

Dalichaouch, Mahieddine January 1989 (has links)
Application of the second law of thermodynamics to refrigeration systems is useful in identifying the thermodynamic losses and in finding out where improvements might be made. Theoretical absorption refrigeration cycles are analysed using the first law-based equations of energy balances and the second law-based concept of lost work. A thermodynamic efficiency, defined and formulated from the lost work approach, is used to examine a lithium bromide -water absorption cooling cycle with hot water as the heat source and cooling water as the heat sink. The cycle parameters are varied over applicable operating ranges in order to find their effect on the cycle thermodynamic efficiency. To accomplish this objective and to make a parameteric analysis for the L iBr -water absorption cycle under steady-state conditions, two computer programmes are written. The results indicate the system might be improved by better design. The efficiency variation is compared to variations of coefficient of performance found in the literature. A LiBT -water absorption refrigeration system for low hot water temperature applications has been proposed and detailed design aspects have been considered. Fabrication and testing of a laboratory model of the absorption refrigeration system have been described. As new design methodologies of solar energy applications have been developed recently, a study of solar thermal systems for absorption refrigeration has been presented. This includes the classification, description and modelling of solar systems. Types of design procedures of solar systems for absorption refrigeration are discussed and a computer programme has been implemented which prints out the yearly solar fraction of a solar thermal system with daily storage for supplying heat to an absorption cooling cycle. Numerical performance tests are carried out and the results show that the phibar-f chart design method is a simple and convenient mean of predicting the thermal performance of solar systems.

An experimental study of heat driven absorption cooling systems

Best Y. Brown, Roberto January 1990 (has links)
The great need for cooling combined with Mexico's large availability of low enthalpy energy from non conventional energy resources such as geothermal energy, solar heat and waste heat from industrial processes, makes it very attractive to utilize these resources for cooling using heat driven absorption systems. The main purpose of the work described in this thesis is to obtain experimental and theoretical data on heat driven absorption cooling systems for the design of large scale systems. Thermodynamic design data have been theoretically derived for heat driven absorption heat pumps and heat transformers using the working pairs ammonia-water and ammonia-lithium nitrate for cooling, heating and simultaneous heating and cooling. The interaction between the operating parameters has been illustrated graphically. A computer model of the steady state thermodynamics of a heat driven ammonia-water system and an ammonia-lithium nitrate system has been developed. A comparison of both systems is made by assessing the effect of operating temperatures and heat exchanger effectiveness on the coefficient of performance for cooling and the heat transfer rates within the system. An experimental study on the performance of the absorber of an absorption cooling system operating on water-lithium bromide has been made. The experimental study of the adiabatic absorber was concerned with the determination of the effect of the evaporator heat load and the absorber reflux on the performance of the absorber. An experimental study of the operating characteristics of an experimental. absorption cooler using water-lithium bromide-lithium iodide and waterlithium bromide-zinc bromide as ternary systems has been made in order to achieve higher coefficients of performance and a lower risk of crystallization. Experimental studies with a small heat driven absorption cooling system operating on ammonia-water using a falling film generator were made. Low generator temperatures were achieved which will'enable the use of non focussing solar collectors as a heat source for the system. An ammonia-water absorption cooler operating on low enthalpy geothermal energy was installed and operated at two geothermal fields. The system was used to cool a small cold storage facility below freezing temperatures. The experimental and theoretical results on absorption cooling systems will provide a basis for the design of heat pump systems for industrial and commercial applications.

Theoretical study of an absorption refrigeration system powered by CPC solar collectors for applications at near equatorial latitudes

Babawale, Z. A. January 1988 (has links)
No description available.

An investigation into the effects of lubricating oil on heat pump evaporator performance and possible cycle improvements utilising a regenerative expansion process

Masson, Alan John January 1989 (has links)
No description available.

Investigation and performance optimisation of multi compressor refrigeration system

Chan, Kuan Yoong January 2002 (has links)
No description available.

Field Measurements and Evaluation of CO2 Refrigeration Systems for Supermarkets

Kullheim, Johan January 2011 (has links)
In this thesis, three supermarket refrigeration systems are evaluated; two trans-critical DX CO2 systems and one R404A/CO2 cascade system. Field measurements of energy consumption, temperatures, pressures, and compressor motor frequency are made using the computer programs IWMAC and LDS. Calculations are performed using the program Refprop and performance data from the compressor manufacturer. The cooling capacity and coefficient of performance (COP) are calculated and the analysis is made for a period of four months during the summer, June-September 2010, for all systems. The results show that the cascade system has a significantly lower value of COP than the trans-critical CO2 systems. This is due to the unusual design and control of the cascade system. The COP also drops because of the extra temperature levels and pumps present in this system. The use of floating condensation and the fact that no pumps are required for refrigerant circulation is beneficial for the trans-critical systems, resulting in higher COP. The operation of the heat recovery systems is investigated and the results suggest some differences in operation between the two trans-critical systems. The influence of system parasites like pumps and fans on system performance is also investigated for the three systems.

The growth of Staphylococcus aureus strain 100 in iceless refrigerator

Alalade, Olufunmike Omotola, January 1969 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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