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Thermophysical Properties of Aqueous Solutions Used as Secondary Working Fluids
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Secondary working fluids (secondary refrigerants, heat transfer fluids, antifreezes, brines) have long been used in various indirect re-frigeration and heat pump systems. Aqueous solutions (water solu-tions) have long been used as single phase (liquid only) secondary working fluids for cooling in supermarkets, ice rinks, heat recovery systems, heat pumps and other applications. However, aqueous solutions are increasingly used also for freezers in supermarkets and other applications in low temperature refrigeration.

Of importance when comparing different secondary working fluids for indirect systems are the following basic thermophysical properties: freezing point, density, viscosity, specific heat, and thermal conductivity. Reliable data of these properties are needed to choose suitable fluid and to make technical calculations of an indirect refrigeration or heat pump system.

The main intention of this work has been to select thermophysical property data with good or acceptable technical accuracy of a number of aqueous solutions that can be used by the refrigeration and heat pump industry, rather than focusing on a limited number of property values or scientifically very accurate measuring techniques.

A thorough literature search was in view of this made to find the most reliable property values of aqueous solutions. Detailed literature references are given for thermo-physical properties of the following aqueous solutions, without other additives: Ethylene and propylene glycol, ethyl and methyl alcohol, glycerol, ammonia, potassium carbonate, calcium, lithium, magnesium and sodium chlorides as well as potassium acetate and potassium formate. Some laboratory measurements were made of most of the fluid types when literature values were incomplete or deemed unreliable. Methods used are briefly described and results are given.

Much of the work was reported on in the Engineering Licentiate Thesis: Thermophysical properties of liquid secondary refrigerants, A Critical Review on Literature References and Laboratory Measure-ments (Melinder 1998a). That material forms the basis for the charts and tables used in the IIR-publication Thermophysical properties of liquid secondary refrigerants (Melinder, 1997). The present thesis reports on an update made since 1998, including re-view work done on two additional fluids not covered in Melinder (1998a).

The thesis describes how the selection of property values results in tables and charts intended for the industry. Coefficients for poly-nomial equations are generated from these property values using a Matlab program and this material is intended as a useful tool for computer treatment. Aqueous solution of ethyl alcohol is used as example to see how this process is made. This choice of fluid can also be seen as a test of this method, as the basic thermophysical properties of aqueous solutions of ethyl alcohol present more chal-lenges than the other fluids examined.

A comparison is made of a few types of aqueous solutions used as secondary working fluids for two types of applications. The first example is bedrock heat pumps and the second is cooling cabinets in a supermarket. An effort is made to see how the additive con-centration affects the thermal performance.

Most aqueous solutions used as single-phase secondary fluids can also be used as ice slurry, a fluid consisting of liquid and ice where small ice crystals are produced, usually with some type of ice generator. The ice crystals are then transported to the cooling object from which heat is removed when ice crystals melt. This results in less temperature change in the cooling object and makes it also possible to reduce the volume flow rate and to use smaller pipe dimensions in the system.

In order to choose a secondary fluid for ice slurry use and to make correct technical calculations of the ice slurry system there is a need to examine and evaluate thermo-physical properties and other aspects of ice and of the aqueous solution used. For dimensioning purposes it is of interest to estimate ice mass fraction and enthalpy values and enthalpy-phase diagrams can serve that purpose. This thesis presents enthalpy-phase diagrams made by author that besides isotherms contain lines with ice fraction and lines connecting enthalpies at freezing point and 1, 2, etc. to 10 K below the freezing point curve.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , xiv, 130 p.
Series
Trita-REFR, ISSN 1102-0245 ; 07/60
Keyword [en]
Secondary working fluids, secondary refrigerants, indirect systems, aqueous solutions, ice slurry, thermophysical properties, freezing point, density, viscosity, specific heat, thermal conductivity
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4406ISBN: 978-91-7178-707-1 (print)OAI: oai:DiVA.org:kth-4406DiVA: diva2:12169
Public defence
2007-06-08, M2, Brinellvägen 64, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100609Available from: 2007-05-29 Created: 2007-05-29 Last updated: 2010-06-09Bibliographically approved
List of papers
1. A Critical Review on Thermophysical Properties of Liquid Secondary Refrigerants
Open this publication in new window or tab >>A Critical Review on Thermophysical Properties of Liquid Secondary Refrigerants
1998 (English)In: Natural Working Fluids '98: proceedings, 1998Conference paper, Published paper (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13277 (URN)
Conference
IIR - Gustav LorentzenConference — meeting of Commissions B1, B2, E1, and E2, Oslo, Norway, 2-5 June1998
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-07-14Bibliographically approved
2. Enthalpy-phase diagrams of aqueous solutions for ice-slurry applications
Open this publication in new window or tab >>Enthalpy-phase diagrams of aqueous solutions for ice-slurry applications
2002 (English)In: Proc. of the Fifth workshop on Ice slurries of the International Institute of Refrigeration, 2002Conference paper, Published paper (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13278 (URN)
Conference
KTH/Stockholm, Sweden, 30-31 May 2002
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-07-14Bibliographically approved
3. Update on Indirect Systems and Secondary Fluids with Focus on Supermarket Refrigeration
Open this publication in new window or tab >>Update on Indirect Systems and Secondary Fluids with Focus on Supermarket Refrigeration
2003 (English)In: FTEC 2003, 2003Conference paper, Published paper (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13280 (URN)
Conference
International Conference on Fluid and Thermal Energy Conversion 2003, Bali, Indonesia
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-07-14Bibliographically approved
4. Comparing properties of aqueous solutions for liquid only and ice slurry applications of indirect systems
Open this publication in new window or tab >>Comparing properties of aqueous solutions for liquid only and ice slurry applications of indirect systems
2003 (English)In: 21st International congress of refrigeration: proceedings, 2003Conference paper, Published paper (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13281 (URN)
Conference
IIR/IIF Washington 2003
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-07-14Bibliographically approved
5. Secondary fluids for low operating temperatures
Open this publication in new window or tab >>Secondary fluids for low operating temperatures
2004 (English)In: 6th IIR-Gustav Lorentzen Natural Working fluids, Glasgow, August 29–September 1, 2004, 2004Conference paper, Published paper (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13282 (URN)
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-07-14Bibliographically approved
6. Using property values of aqueous solutions and ice to estimate ice concentrations and enthalpies of ice slurries
Open this publication in new window or tab >>Using property values of aqueous solutions and ice to estimate ice concentrations and enthalpies of ice slurries
2005 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 28, no 1, 13-19 p.Article in journal (Refereed) Published
Abstract [en]

For ice slurry calculations and modeling, it is important that they are performed with accurate thermophysical property values of the aqueous solution and of ice. For ice slurry applications there is a need for accurate freezing point data and for more basic thermophysical property data at low concentrations. The article covers some phenomena in connection with freezing of aqueous solutions. Charts with ice concentration curves as a function of temperature and additive concentration are given for a number of aqueous solutions. A main purpose of using ice slurry is to benefit from the latent heat or enthalpy difference at melting. The article shows how an enthalpy-phase diagram can be constructed, gives charts with enthalpy values and charts giving apparent specific heat as a function of temperature and concentration for aqueous solution of propylene glycol, ethyl alcohol and potassium formate. These charts for ethyl alcohol-water are in good agreement with works earlier reported on.

National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13286 (URN)10.1016/j.ijrefrig.2004.07.013 (DOI)000226142900003 ()2-s2.0-10044226135 (Scopus ID)
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-06-09Bibliographically approved
7. Properties of various secondary fluids for supermarket applications
Open this publication in new window or tab >>Properties of various secondary fluids for supermarket applications
2005 (English)In: IIR International Conference Thermophysical Properties and Transfer Processes of Refrigerants, Refrigeration Science and Technology Proceedings: Commercial Refrigeration/Thermophysical Properties and Transfer Processes of Refrigerants, 2005 August 31–September 2; Vicenza, Italy, 2005Conference paper, Published paper (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13283 (URN)
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-06-09Bibliographically approved
8. Updating and extending secondary fluid data for various refrigeration and heat pump applications
Open this publication in new window or tab >>Updating and extending secondary fluid data for various refrigeration and heat pump applications
2006 (English)In: GLC 2006 Trondheim, 2006Conference paper, Published paper (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13284 (URN)
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-06-09Bibliographically approved
9. Equilibrium properties of ice slurry based on two chosen types of aqueous solutions
Open this publication in new window or tab >>Equilibrium properties of ice slurry based on two chosen types of aqueous solutions
2006 (English)In: 7th IIR Conference on Phase Change materials and Slurries for Refrigeration and Air Conditioning , Dinan, France, 2006Conference paper, Published paper (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-13285 (URN)
Note
QC 20100609Available from: 2010-06-09 Created: 2010-06-09 Last updated: 2010-06-09Bibliographically approved

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