Single-Phase and Two-Phase Secondary Coolants: Simulation and Evaluation of Their Thermophysical Properties (original) (raw)
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Thermo-Physical Properties of Aqueous Solution of Ice Slurry
2018
In the last decade, ice slurry gained much attention as a cooling medium due to its high energy storage capacity and transportability. However the flow of ice slurry is a complex phenomenon as it affected by various parameters and properties of aqueous solution. In the present work the variation of different thermo-physical properties viz. density, freezing point temperature and viscosity of aqueous solution with different freezing point depressant (FPD) has been calculated and analyzed. The comparison shows that ethanol (EA) is the best candidate as a FPD among ethylene glycol (EG), propylene glycol (PG) and sodium chloride.
Comparison of the performance of different ice slurry types depending on the application temperature
International Journal of Refrigeration-revue Internationale Du Froid, 2006
The ice slurry medium type used in a refrigeration application could influence the performance of an ice slurry system. For this reason and depending on the refrigeration application, the user has to usually carry out a judgemental selection of the ice slurry mixture type, which should take into account the solute type and its concentration. This article compares the performance of several commonly used organic and inorganic ice slurry secondary refrigerants. This study was based on thermophysical assessments carried out at different operating temperatures. The calculation method that was used to determine the ice slurry properties is first presented. Then, in order to describe the thermophysical efficiency of mixtures at various operating temperatures (K5, K20 and K35 8C), three performance criteria were compared, namely, the volume enthalpy drop, the temperature at the inlet of the application and the relative viscosity of the ice slurry. The results showed that inorganic mixtures are good selection candidates, except for situations where low temperatures and high ice concentrations are encountered at the inlet of the application. Methyl alcohol came out as a good performance candidate for all refrigeration applications, although NH 3 was the best choice based on the current thermo-physical property assessments. q Performances de plusieurs types de coulis de glace selon la température utilisée: comparaison Résumé Le développement de la technologie des coulis de glace est étroitement lié à l'efficacité énergétique du fluide utilisé. Cette performance énergétique dépend de nombreux paramètres tels que la nature du soluté utilisé, sa concentration et la fraction massique en glace adoptée en entrée d'application. Ainsi, chaque type d'application industrielle peut nécessiter le choix d'un (J. Guilpart).
From physical properties of ice slurries to industrial ice slurry applications
International Journal of Refrigeration, 2005
The use of ice slurries dates back many millenniums, e.g. the ancient Romans applied the cooling of snow-water and icewater mixtures. Approximately two decades ago a breakthrough of the new technology of producing ice slurries has set in the refrigeration domain for the cooling of shops and supermarkets. After some difficulties at the beginning, it is now possible to build systems, which operate as designed. However, there is still a huge potential to lower the energy consumption and the costs of the systems. Actions in this direction are the design of new ice slurry generators, the development of new concepts for storage and mixing, etc. In this article a short review of the basic research on ice slurries is presented. Furthermore, practical problems of the application of the technology in refrigeration and process techniques are discussed. q (P.W. Egolf).
Thermodynamics and heat transfer of ice slurries
International Journal of Refrigeration, 2005
The thermodynamics and heat transfer of ice slurries is reviewed. It starts with a collection of models to calculate the effective thermal conductivity. These relations were derived for suspensions with solid particles that do not change its phase. Therefore, they can only be first approximations. Then dimensionless numbers are introduced, once based on the physical properties of the carrier fluid and then also on the macroscopic fictious physical properties of the ice slurries. Both sets of quantities show their specific advantages. With this information the basic definitions of heat transfer are introduced. Then existing measurements and calculations of heat transfer coefficients-respectively of its dimensionless counterpart, the Nusselt number-are discussed in detail. q
Ice slurry – History, current technologies and future developments
International Journal of Refrigeration, 2019
Ice Slurry is an exciting fluid. It is often called a secondary refrigerant or a heat transfer fluid, because it does not evaporate inside the heat exchanger like refrigerants do. But looking at the energy density and the heat transfer characteristics, ice slurry is on eye level with many HFC refrigerants. Ice slurry can be used inside heat exchangers and in direct contact cooling, offering many interesting areas such as fish or produce chilling. In addition, it can be used for pipe cleaning or for pushing (pigging) precious products out of pipes without significant product loss. Ice slurry has evolved from a niche product into a technology applied in many fields. Nonetheless, developing efficient ice slurry production, effective ice slurry storage and reliable ice and additive concentration measurements as well as crystal growth issues remain challenging tasks for engineers. The paper suggests future research.
Experimental Thermal and Fluid Science, 2012
Experiments were conducted in a shell and tube heat exchanger with an ethylene glycol ice slurry flowing in the tubes and hot water in the shell. Pressure loss in the tubes, inlet and outlet density for the ice slurry, in addition to inlet temperature, outlet temperature and mass flowrate for both fluids were measured. A transient study with a slurry flowrate of 10 kg/min and water flowrate of 5 kg/min revealed that, when the ice concentration increases from 0 to 0.25 kg/kg, the heat transfer coefficient increases by 33% and the effectiveness increases by 18%. However, the pressure loss also increases by a factor of 2.3. The rate of increase of the heat transfer coefficient with mass flowrate is greater for a single phase fluid than for the ice slurry. The ice concentration has a greater impact on the heat transfer coefficient when the flowrate of the ice slurry is low. Overall heat transfer coefficients evaluated using two methods and twenty-one different correlations for the ice slurry were compared to values obtained from an energy balance. The most accurate results for turbulent flow were obtained using the Bell-Delaware method and the Colburn or Gnielinski correlations. For laminar flow the combination of Kern's method with the correlation by Shah gave the best predictions of the overall heat transfer coefficient. The rate of increase of the pressure loss with ice concentration is small for concentrations between 0 and 0.15 kg/kg but increases for higher ice concentrations. Pressure losses calculated with several ice slurry correlations were compared to measured values. The more accurate correlations were those of Filonenko, Drew-Koo-McAdams and Blasius. The measured values indicate that at the outlet of the heat exchanger the solid and liquid phases are not in thermodynamic equilibrium; in fact ice exists for liquid temperatures higher than the melting temperature.
Thermo-Fluidic Characteristics of Two-Phase Ice Slurry Flows Based on Comparative Numerical Methods
Processes, 2019
Ice slurry is a potential secondary refrigerant for commercial refrigeration systems because of its remarkable thermal properties. It is necessary to optimize the heat transfer process of ice slurry to reduce the energy consumption of the refrigeration system. Thus, this study investigates the heat transfer performance of single-phase (aqueous solution) and two-phase (ice slurry) refrigerants in a straight horizontal tube. The numerical simulations for ice slurry were performed with ice mass fraction ranging from 5% to 20%. The effects of flow velocity and ice concentration on the heat transfer coefficient were examined. The results showed that heat transfer coefficient of ice slurry is considerably higher than those of single-phase flow, particularly at high flow velocity and ice content, where increase in heat transfer with a factor of two was observed. The present results confirmed that ice slurry heat transfer ability is considerably affected by flow velocity and ice concentration in laminar range. Moreover, the second part of this paper reports on the credibility three distinct two-phase Eulerian-Eulerian models (volume of fluid (VOF), mixture, and Eulerian) for the experimental conditions reported in the literature. All two-phase models accurately predict the thermal field at low ice mass fraction but underestimate that at high ice mass fractions. Regardless of the thermal discrepancies, the Eulerian-Eulerian models provide quite reasonable estimation of pressure drop with reference to experimental data. The numerical predictions from the VOF model are more accordant with the experimental results and the maximum percentage error is limited tõ 20% and~13% for thermal and pressure drop predictions, respectively.
Experimental study of the thermal characteristics of phase change slurries for active cooling
Applied Energy, 2012
Phase change materials (PCMs) are increasingly being used for thermal energy storage in buildings and industry to produce energy savings and reduce carbon dioxide emissions. PCM slurries are also being investigated for active thermal energy storage or as alternatives to conventional single phase fluids because they are pumpable and have advanced heat transport performance with phase change. The present study investigates several types of phase change materials for the preparation of PCM slurries which have potential for cooling applications. The thermophysical properties of paraffin in water emulsions, such as latent heat of fusion, melting and freezing temperature ranges, viscosity and the effect of surfactants, have been tested using appropriate experimental techniques. It has been identified that the use of small quantities of higher melting temperature paraffin and surfactants in the emulsion can reduce the effect of supercooling and increase the useful heat of fusion. However there are negative impacts on viscosity which should be considered in heat transport applications.
Heat Transfer Characteristic in Ice Slurry Generator
2004
New ice crystal slurry generator system, for thermal energy storage (TES), has been developed for both air conditioning and cooling process applications. The system uses a scraped-surface orbital rod evaporator (ORE), a vertical shell-and-tube heat exchanger with mechanical heat transfer augmentation, as a dynamic icemaker to generate "liquid ice". Ice forms continuously without accumulation inside the ORE and is compatible with conventional condensing units, storage tanks and pumps. Diluted aqueous solution or non-organic brine solutions promote ice crystals formation. The cooling load circuit can be hydraulically decoupled from ice production at the storage tank. This way, the hydraulic system of refrigeration, responsible for providing the thermal load, can work independently of the ice production, utilizing the stored slurry. Stored ice slurry provides consistently low temperatures over significant portions of the ice melt period and may be melted very rapidly due to the large surface area. With its characteristic high evaporator temperatures and high heat fluxes, the systems have the potential to significantly reduce the capital and operating costs, when compared with static ice or ice harvesting technologies. Overall heat transfer coefficients are measured experimentally and compared with similar configurations without phase change.