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- Grozdek, Marino, et al.
(författare)
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Experimental investigation of ice slurry heat transfer in horizontal tube
- 2009
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Ingår i: International journal of refrigeration. - : Elsevier BV. - 0140-7007 .- 1879-2081. ; 32:6, s. 1310-1322
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Ignatowicz, Monika, 1983-, et al.
(författare)
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Alternative formate salts as low temperature secondary fluids
- 2017
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Ingår i: 5Th Iir International Conference On Thermophysical Properties And Transfer Processes Of Refrigerants (Tptpr). - : INT INST REFRIGERATION. ; , s. 443-450
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Konferensbidrag (refereegranskat)abstract
- Potassium organic salts like formates and acetates are known as environmentally friendly secondary fluids. The most important advantages of salts compared to aqueous solutions of alcohols and glycols are good thermophysical properties, low toxicity and non-flammability. The purpose of this work is to investigate properties of different formate salt based secondary fluids like: lithium formate, ammonium formate and sodium formate at low temperatures in order to propose new blends of formate salts that could be used as secondary fluids for low temperature applications. Studies showed that different alkali metal ions like sodium, lithium or ammonium are affecting the solubility level, freezing point, thermal conductivity, dynamic viscosity and specific heat capacity in different way. Among examined formate salts, ammonium formate showed the best performance by giving the lowest freezing point as well as the highest specific heat capacity and highest thermal conductivity and similar dynamic viscosity. Lithium formate salts had the highest dynamic viscosity among all samples and despite high specific heat capacity and thermal conductivity values these salts cannot be recommended for low temperature applications. 30 wt-% sodium formate and 36 wt-% lithium formate were recrystallizing at lower temperatures than 0 degrees C when fast cooling rate was applied. Thus, the possible application for these salts is rather limited to higher temperatures only. As seen, different type of cation group in the formate salt can result in different properties, thus, further studies to investigate ammonium formate as well as different acetate salts are recommended.
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| 5. |
- Ignatowicz, Monika, 1983-, et al.
(författare)
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Cesium and ammonium salts as low temperature secondary fluids
- 2019
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150357 ; , s. 2568-2575
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Konferensbidrag (refereegranskat)abstract
- Potassium formate and potassium acetate, as well as their blends are known as environmentally friendly secondary fluids with good thermophysical properties. The aim of this work was to investigate properties of cesium formate, cesium acetate and ammonium acetate solutions. Results showed that various alkali metal ions such as potassium, sodium, cesium or ammonium are affecting the freezing point, thermal conductivity, viscosity and specific heat capacity in different ways. Among examined salts, ammonium formate showed the best performance by giving the highest specific heat capacity and highest thermal conductivity and the lowest dynamic viscosity compared to potassium formate and other salts. Cesium formate solutions had the lowest viscosity among all tested salts. This study shows that both cesium formate and sodium formate could be used as different additives to enhance different properties of potassium formate and potassium acetate secondary based fluids.
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| 6. |
- Ignatowicz, Monika, et al.
(författare)
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Ethyl and isopropyl alcohol blends as alternative secondary fluids
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 2224-2231
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Konferensbidrag (refereegranskat)abstract
- Methyl and ethyl alcohol based secondary fluids are commonly used in different indirect refrigeration systems due to relatively good thermophysical properties. Methyl alcohol is considered toxic and not permitted for use as secondary fluid in most of Europe. Ethyl alcohol based secondary fluids are commonly used in Sweden due to their low toxicity and good properties. Commercially available ethyl alcohol based fluids contain up to 10 wt-% denaturing agents in form of propyl alcohol (2-propanol, isopropanol) and nbutyl alcohol (n-butanol). Results show that presence of propyl alcohol in the ethyl alcohol based secondary fluid improves its thermophysical properties such as specific heat capacity, thermal conductivity and dynamic viscosity when added in small concentration. The aim of this paper is to investigate the thermophysical properties of various ethyl and isopropyl alcohol blends in order to find the most optimal blend as well as to evaluate if this blend could become a competitive alternative secondary fluid.
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| 7. |
- Ignatowicz, Monika, et al.
(författare)
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Evaluation of thermophysical properties of ethyl alcohol based secondary fluids
- 2014
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Ingår i: 11th IIR Gustav Lorentzen Conference on Natural Refrigerants. - 9782362150043 ; , s. 100-107
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Konferensbidrag (refereegranskat)abstract
- Ethyl alcohol (ethanol) based secondary fluids are commonly used in different types of indirect refrigeration systems in Scandinavia due to low toxicity, relatively good thermophysical properties and environmental regulations regarding leakage. Ethyl alcohol based commercial products available in Scandinavia contain different types of denaturing agents but no corrosion inhibitors. The most common denaturing agents are isopropyl alcohol (isopropanol), n-butyl alcohol (n-butanol), methyl ethyl ketone and methyl isobutyl ketone. Property measurements recently performed at KTH showed that presence of these additives in ethyl alcohol based secondary fluid improved thermophysical properties especially in terms of specific heat, thermal conductivity, and dynamic viscosity. Additionally, it was found that the specific heat capacity tendency is different than previously reported.
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| 8. |
- Ignatowicz, Monika, 1983-, et al.
(författare)
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ISO-PARAFFINS AS LOW TEMPERATURE SECONDARY FLUIDS
- 2017
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Ingår i: 5TH IIR INTERNATIONAL CONFERENCE ON THERMOPHYSICAL PROPERTIES AND TRANSFER PROCESSES OF REFRIGERANTS (TPTPR). - : INT INST REFRIGERATION. ; , s. 436-442
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Konferensbidrag (refereegranskat)abstract
- Ethylene and propylene glycol water based secondary solutions are very popular due to their low corrosivity character, low freezing point, high boiling point and low fire hazards. The main drawback of ethylene glycol solutions is its potential toxicity both to the environment, animals and food products. Therefore, propylene glycol is the most common substitute for ethylene glycol. The biggest disadvantage of propylene glycol solutions is its very high viscosity at low temperatures, which results in higher pumping power and lower system performance. For very low temperatures, it is common to use non-aqueous synthetic fluids, which have lower viscosities at these temperatures. Thus, the aim of this paper is to propose a new generation of synthetic iso-paraffins having better thermophysical properties compared to existing synthetic products used for very low temperature applications. The first results showed that the new generation of iso-paraffins having the freezing temperature of - 50 degrees C or lower had significantly lower viscosity (between 75 % and 98 %) at very low temperatures compared to 60 wt-% propylene glycol (PG 60 %) and 60 wt-% ethylene glycol solution (EG 60 %). Iso-paraffin 1 showed better performance than iso-paraffin 2 by giving the lowest freezing point, the lowest dynamic viscosity and kinematic viscosity as well as the highest thermal conductivity. Instead, iso-paraffin 2 had higher specific heat capacity. As seen, the different composition of iso-paraffin mixture can result in different properties and operating temperature ranges. Thus, iso-paraffins could become an interesting alternative for very low temperature cooling applications.
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| 9. |
- Ignatowicz, Monika, et al.
(författare)
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MEASUREMENTS OF STANDARD SEAWATER CALLS FOR MINOR ADJUSTMENTS OF SEAWATER ICE SLURRY PROPERTIES
- 2016
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Ingår i: 11TH IIR CONFERENCE ON PHASE CHANGE MATERIALS AND SLURRIES FOR REFRIGERATION AND AIR CONDITIONING. - 9782362150159 ; , s. 162-170
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Konferensbidrag (refereegranskat)abstract
- Seawater is the most common fluid on earth and ice generating machines are increasingly used on fishing vessels to produce ice slurry from the seawater with up to 60 % ice to be poured over the catch. In this study, new measurements of thermophysical properties of standard seawater have been carried out to complement a recent literature search made to establish thermophysical property data of seawater as function of salinity and temperature. These single-phase measurements have been made for salinity 20, 30 and 35 g kg(-1) (2.0, 3.0 and 3.5 % total salt content) and include measurements of freezing point, density, dynamic viscosity, thermal conductivity, specific heat capacity and specific enthalpy. The obtained experimental results generally confirm recent literature search and experimental results only call for minor adjustments of viscosity values. Hence, experimental results confirm the following published ice slurry properties: enthalpy, ice fraction and ice slurry density.
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| 10. |
- Ignatowicz, Monika, 1983-, et al.
(författare)
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Methods of BHE flushing, charging and purging in Sweden
- 2016
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Ingår i: Proceedings.
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Konferensbidrag (refereegranskat)abstract
- In Sweden, there are more than 500 000 small and about 500 relatively large ground source heat pumps (GSHP) having a total installed capacity of about 5.6 GW delivering approximately 15 TWh. yr-1 of heating and cooling energy in Sweden. The operational lifetime and reliability of any GSHP depends heavily on the way the system is designed, installed and operated. In order to provide a good system performance after installation, aspects such as borehole heat exchanger (BHE) system flushing, charging and purging, among others, should be taken into consideration. The aim of this work has been to review some existing methods of system flushing, charging and purging in order and make observations that may be applicable for the GSHP industry. Two Swedish case studies have been followed up and compared to existing strategies suggested by IGSHPA.The results show that there is a lack of specific recommendations regarding the flushing and purging procedures for BHEs in Sweden. A well-defined range or adaptation of similar IGSHPA standards could help in defining the minimum flush velocity. The two case studies showed different practices, with flushing velocities being significantly higher than the minimum flushing velocity recommended by IGSHPA. Flushing flow rates based on this standard are presented in this work for some typical BHE pipe sizes used in Europe.
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