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Load Shifting and Storage of Cooling Energy through Ice Bank or Ice Slurry Systems: modelling and experimental analysis
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ice based Cool Thermal Energy Storage (CTES) systems have attracted much attention during last few decades. The reasons are mainly of economical and environmental nature. Compared to conventional refrigeration and air-conditioning systems without cool thermal energy storage, implementation of CTES will increase environmental standards and overall efficiency of the energy systems as it contributes to the phase-out of synthetic refrigerants and reduces peak loads in electricity grids.

For the application of a cool thermal energy storages in refrigeration installations and HVAC systems in industry and building sector, it is necessary to have appropriate design tools in order to sufficiently accurate predict their performance. In this thesis theoretical and experimental investigations of two ice based cool thermal energy storage systems, namely static, indirect, external melt, ice-on-coil, i.e. ice bank system and dynamic, ice slurry cool thermal energy storage system are carried out.

An ice bank storage technology for cooling purposes is known for a long time. The main drawbacks which are hindering its wider use are the system complexity, high first costs, system efficiency which is highly dependant on design, control and monitoring of the system, etc. On the other hand, ice slurry technology was not well studied until recently, while in the current scientific literature there are still differences between results and conclusions reported by different investigators.

The aim of the present thesis is to extend the knowledge in the field of ice based CTES systems, thereby contributing in the development and wider utilization of those systems.

In the first part of the thesis a computer application, named “BankaLeda” is presented. It enables simulation of an ice bank system performance. In order to verify developed simulation model an experimental evaluation has been performed. Field measurements have been conducted on a two module silo which was installed as a part of the refrigeration system in dairy and cheese factory “Antun Bohnec” in the city of Ludbreg in Croatia. Experimental findings were compared to the simulation model. The software „BankaLeda“ presents a strong optimization tool for designers and engineers in the field by providing a high degree of freedom in defining particular system design and operating parameters. It offers a basis for assessment and testing of a new energy efficient system arrangements and measures. Besides it will give decisionmakers the ability to test potential solutions in the process of CTES system design.

In the second part of the thesis ice slurry pressure drop and heat transfer in horizontal straight tubes have been experimentally investigated. In particular a mixture of 10.3 % of ethanol and water with an initial freezing point of -4.4 °C was considered. It was found that the behaviour of ice slurry flow is changing with time and that ice slurry pressure drop is generally higher than for single phase flow. However for ice concentrations of 15 % and higher, for certain velocities ice slurry pressure drop is found to be of a similar value as for single phase fluid. Moreover, if ice slurry is to be used as a energy transport media it is recommended to keep the ice mass fraction at a level of 20 %.

With tube geometry and thermophysical properties of a carrier fluid the heat transfer of ice slurry is generally a function of ice mass fraction and velocity. The imposed heat flux has no or has just minor influence on the heat transfer coefficient. Up to ice mass fraction between 10-15 % the mean heat transfer coefficient shows only slight (laminar flow) or no increase (turbulent flow) in comparison to single phase flow. Beyond that ice mass fraction the heat transfer coefficient is increasing significantly.

The test data for pressure drop and heat transfer in laminar and turbulent regime was compared to several correlations from the literature. A new correlations for ice slurry pressure drop and heat transfer in the laminar flow regime, for 10.3 % ethanol and water mixture, were derived based on the present experimental data. The correlation for pressure drop predicts 82 % of the experimental data with ±15 % accuracy, while the correlation for heat transfer predicts 75 % of the data with the same accuracy.

In order to investigate advantages and disadvantages of a dynamic, ice slurry system over a static, indirect, external melt, ice-on-coil CTES system and to assess their differences from economical aspects, a theoretical simulation model of an ice slurry CTES have been developed. It was found that the ice slurry based CTES systems posses higher economic and energy saving potential than static type systems. In the best case scenario the total energy consumption of dynamic CTES system was found to be approximately 25 % lower than for a static CTES system.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , x, 196 p.
Series
Trita-REFR, ISSN 1102-0245 ; 09:62
Keyword [en]
refrigeration systems, cool thermal energy storage system, ice, modelling, simulation, field measurement, experiment, indirect system, ice-on-coil system, external melt, ice slurry, homogeneous storage, heterogeneous storage
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11119ISBN: 978-91-7415-434-4 (print)OAI: oai:DiVA.org:kth-11119DiVA: diva2:236431
Public defence
2009-10-16, F3, Lindstedtsvägen 26, Kungliga Tekniska Högskolan, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20100715Available from: 2009-09-25 Created: 2009-09-21 Last updated: 2010-07-15Bibliographically approved
List of papers
1. Experimental Investigation of an Ice Bank System Performance
Open this publication in new window or tab >>Experimental Investigation of an Ice Bank System Performance
2009 (English)In: 3rd IIR Conference on Thermophysical Properties and Transport Processes of Refrigeration, Boulder, Colorado, USA, 2009, 2009Conference paper, Published paper (Other academic)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14122 (URN)
Note
QC 20100714Available from: 2010-07-14 Created: 2010-07-14 Last updated: 2010-07-15Bibliographically approved
2. Development of computer program for simulation of an ice bank system operation, Part I: Mathematical modelling
Open this publication in new window or tab >>Development of computer program for simulation of an ice bank system operation, Part I: Mathematical modelling
2009 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 32, no 6, 1323-1335 p.Article in journal (Refereed) Published
Abstract [en]

Since the use of standard engineering methods in the process of an ice bank performance evaluation offers neither adequate flexibility nor accuracy, the aim of this research was to provide a powerful tool for an industrial design of an ice storage system allowing to account for the various design parameters and system arrangements over a wide range of time varying operating conditions. In this paper the development of a computer application for the prediction of an ice bank system operation is presented. Static, indirect, cool thermal storage systems with external ice on coil building/melting were considered. The mathematical model was developed by means of energy and mass balance relations for each component of the system and is basically divided into two parts, the model of an ice Storage system and the model of a refrigeration unit. Heat transfer processes in an ice silo were modelled by use of empirical correlations while the performance of refrigeration unit components were based on manufacturers data. Programming and application design were made in Fortran 95 language standard. Input of data is enabled through drop down menus and dialog boxes, while the results are presented via figures, diagrams and data (ASCII) files. In addition, to demonstrate the necessity for development of simulation program a case study was performed. Simulation results clearly indicate that no simple engineering methods or rule of thumb principles could be utilised in order to validate performance of an ice bank system properly.

Keyword
Energy storage, Ice bank, Modelling, Design, Software
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14123 (URN)10.1016/j.ijrefrig.2009.01.011 (DOI)000269466700021 ()
Note
QC 20100714Available from: 2010-07-14 Created: 2010-07-14 Last updated: 2017-12-12Bibliographically approved
3. Experimental investigation of ice slurry flow pressure drop in horizontal tubes
Open this publication in new window or tab >>Experimental investigation of ice slurry flow pressure drop in horizontal tubes
2009 (English)In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 33, no 2, 357-370 p.Article in journal (Refereed) Published
Abstract [en]

Pressure drop behaviour of ice slurry based on ethanol-water mixture in circular horizontal tubes has been experimentally investigated. The secondary fluid was prepared by mixing ethyl alcohol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature -4.4 degrees C). The pressure drop tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 30% depending on test conditions. Results from flow tests reveal much higher pressure drop for higher ice concentrations and higher velocities in comparison to the single phase flow. However for ice concentrations of 15% and higher, certain velocity exists at which ice slurry pressure drop is same or even lower than for single phase flow. It seems that higher ice concentration delay flow pattern transition moment (from laminar to turbulent) toward higher velocities. In addition experimental results for pressure drop were compared to the analytical results, based on Poiseulle and Buckingham-Reiner models for laminar flow, Blasius. Darby and Melson, Dodge and Metzner, Steffe and Tomita for turbulent region and general correlation of Kitanovski which is valid for both flow regimes. For laminar flow and low buoyancy numbers Buckingham-Reiner method gives good agreement with experimental results while for turbulent flow best fit is provided with Dodge-Metzner and Tomita methods. Furthermore, for transport purposes it has been shown that ice mass fraction of 20% offers best ratio of ice slurry transport capability and required pumping power.

Keyword
Ice slurry, Pressure drop, Cold thermal energy storage
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14124 (URN)10.1016/j.expthermflusci.2008.10.003 (DOI)000263207800021 ()2-s2.0-58149312968 (Scopus ID)
Note
QC 20100714Available from: 2010-07-14 Created: 2010-07-14 Last updated: 2017-12-12Bibliographically approved
4. Experimental investigation of ice slurry heat transfer in horizontal tube
Open this publication in new window or tab >>Experimental investigation of ice slurry heat transfer in horizontal tube
Show others...
2009 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 32, no 6, 1310-1322 p.Article in journal (Refereed) Published
Abstract [en]

Heat transfer of ice slurry flow based on ethanol-water mixture in a circular horizontal tube has been experimentally investigated. The secondary fluid was prepared by mixing ethanol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature -4.4 degrees C). The heat transfer tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 22% depending on test performed. Measured heat transfer coefficients of ice slurry are found to be higher than those for single phase fluid, especially for laminar flow conditions and high ice mass fractions where the heat transfer is increased with a factor 2 in comparison to the single phase flow. In addition, experimentally determined heat transfer coefficients of ice slurry flow were compared to the analytical results, based on the correlation by Sieder and Tate for laminar single phase regime, by Dittus-Boelter for turbulent single phase regime and empirical correlation by Christensen and Kauffeld derived for laminar/turbulent ice slurry flow in circular horizontal tubes. it was found that the classical correlation proposed by Sieder and Tate for laminar forced convection in smooth straight circular ducts cannot be used for heat transfer prediction of ice slurry flow since it strongly underestimates measured values, while, for the turbulent flow regime the simple Dittus-Boelter relation predicts the heat transfer coefficient of ice slurry flow with high accuracy but only up to an ice mass fraction of 10% and Re-cf > 2300 regardless of imposed heat flux. For higher ice mass fractions and regardless of the flow regime, the correlation proposed by Christensen and Kauffeld gives good agreement with experimental results. (C) 2009 Elsevier Ltd and IIR. All rights reserved.

Keyword
Thermal storage, Ice slurry, Experiment, Heat transfer, Horizontal tube
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14125 (URN)10.1016/j.ijrefrig.2009.01.014 (DOI)000269466700020 ()2-s2.0-67949120413 (Scopus ID)
Note
QC 20100714Available from: 2010-07-14 Created: 2010-07-14 Last updated: 2017-12-12Bibliographically approved
5. The economic justification of ice storage application in cooling systems within the process industry and building sector
Open this publication in new window or tab >>The economic justification of ice storage application in cooling systems within the process industry and building sector
(English)Article in journal (Other academic) Submitted
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14129 (URN)
Note
QS 20120326Available from: 2010-07-15 Created: 2010-07-15 Last updated: 2012-03-26Bibliographically approved
6. Performance Comparison of a Static Ice-Bank and Dynamic Ice Slurry Cool Thermal Energy Storage Systems
Open this publication in new window or tab >>Performance Comparison of a Static Ice-Bank and Dynamic Ice Slurry Cool Thermal Energy Storage Systems
Show others...
(English)Article in journal (Other academic) Submitted
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14130 (URN)
Note
QS 20120326Available from: 2010-07-15 Created: 2010-07-15 Last updated: 2012-03-26Bibliographically approved

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