Ice Slurry Flow Research Articles

Experimental study on pressure drop and ice blockage characteristics of ice slurry flow in big-diameter pipes

Ice slurry utilization in district cooling brings about attractive reduction in both the storage volume and transportation power of the cold thermal energy. However, the ice slurry flow characteristics, particularly in big-diameter pipes, remains unclear, hindering the application of ice slurry in large-scale district cooling systems. This paper prepared the ice slurry from pure water without any additives to experimentally study its flow characteristics in big-diameter pipes, including DN50, DN80, DN100 and DN190 pipes. The normalized pressure drops and friction factors have been obtained at various velocities and ice fractions. Generally, the pressure drop characteristics did not conform to the Blasius correlation which could predict the single-phase flow until the Reynolds number exceeded a certain threshold, known as the transition Reynolds number. The transition Reynolds numbers were in the range of 3.91 × 104–6.77 × 104 depending on the ice volume fractions ranging from 5% to 21% in the present study. Some visualization measures have been employed to help to observe the flow pattern and confirm the occurrence of ice blockage which was found nowhere but in the branches and expansion. The ice blockage occurred intermittently in the branches, whereas it was irreversible in the expansion. The critical velocity at which the ice blockage began to occur was quantitatively determined, which increased with increasing the ice volume fraction. This study provides a guide for evaluating the pump power and transportation safety of the ice slurry flow in big-diameter pipes.

Particle Dynamics Study on Influencing Factors of Ice Slurry Flow Characteristics in District Cooling Systems

In district cooling systems, substituting the conventional cooling medium with ice slurry represents an ideal approach to achieve economical operation. During pipeline transportation, ice slurry exhibits heterogeneous flow characteristics distinct from those of pure fluids. Consequently, investigating the flow field characteristics of non-homogeneous ice slurry, quantitatively analyzing the rheological variations and flow resistance laws due to the uneven distribution of ice particles, and standardizing the comprehension and depiction of flow patterns within ice slurry pipes hold significant theoretical importance and practical value. This study analyzes the heterogeneous isothermal flow characteristics of ice slurry in a straight pipe by employing particle dynamics and the Euler–Euler dual-fluid model. Taking into account the impact of ice particles’ non-uniform distribution on the rheological properties of ice slurry, a particle concentration diffusion equation is incorporated to develop an isothermal flow resistance model for ice slurry. The flow behavior of ice slurry with initial average ice particle fractions (IPFs) ranging from 0% to 20% in DN20 horizontal straight and elbow pipes is examined. The findings reveal that the degree of heterogeneous flow in ice slurry is inversely proportional to the initial velocity and directly proportional to the initial concentration of ice particles. When the flow velocity is close to 0.5 m/s, the flow resistance of ice particles exhibits a linear positive correlation with changes in flow velocity, whereas the flow resistance of the fluid-carrying phase displays a linear negative correlation. As the flow rate increases to 1 m/s, the contribution of each phase to the total flow resistance becomes independent of the initial velocity parameter. Additionally, the drag fraction of the ice particle phase is positively associated with the initial concentration of ice particles. Furthermore, the phenomenon of “secondary flow” arises when ice slurry flows through an elbow, enhancing the mixing of ice particles with the carrier fluid. The extent of this mixing intensifies with a decrease in the turning radius and an increase in the initial velocity.

Effects of solutes and additives on ice growth prevention in ice slurry production

Ice slurry is a promising functional fluid with high thermal energy density and high heat transfer rate. However, large ice particles in the ice slurry can cause blocking of tubes during ice slurry flow. Therefore, it is preferable to use fine ice particles to prepare ice slurry in many fields. In this study, ice slurries were generated from supercooled solutions containing additives, such as anti-freeze protein and polyvinyl alcohol, to prevent the increase in the ice particle size in the formation process of the ice slurry. The concentration of the solute and amount of the additive were varied as experimental parameters, and the size of the ice particles was evaluated. The average area of the ice particles decreased with the addition of the additives. In particular, anti-freeze protein was effective for generating fine ice particles in the ice slurry. However, the effects of the additives became weaker for higher concentration of the solute, and the size of the ice particles was almost the same regardless of the concentration of the solute and the amount of the additive. Moreover, it was found that particular properties, such as the freezing-point depression, kinematic viscosity of the solution, and effective latent heat of fusion, did not affect the size of the ice particles in the ice slurry generation process.

Study on effects of anti-freeze protein and polyvinyl alcohol on the production and flow behavior of ice slurry

Ice slurry is a promising functional fluid with high thermal energy density and high heat transfer rate. However, the agglomeration of the ice particles in flowing ice slurry can cause blocking of tubes. In this study, anti-freeze protein (AFP) and polyvinyl alcohol (PVA) were selected as additives to prevent the agglomeration of ice particles in ice slurry. Ice slurry was generated using the release of the supercooled state of 3 mass% NaCl solution containing the additives. The size of the ice particles in the ice slurry was observed, and the average area of the ice particles was evaluated to reveal the effects of the additives on the ice particle size. Furthermore, the flow behavior of the ice slurry in a tube was observed, and the effects of the additives on the flow behavior and prevention of the agglomeration of the ice particles were evaluated experimentally. It was found that the average area decreased with increasing concentration of the additives, and the effect of AFP on the average area was particularly significant. In the case of without the additives, the ice particles flowed in the tube while the ice particles agglomerated. On the other hand, the ice particles in the ice slurry with the additives flowed without agglomeration in the tube, especially in the case of AFP addition. It was found that AFP prevented the agglomeration of the ice particles in the ice slurry flow. Moreover, the ice slurries with AFP show the significant tendency for pseudo-plastic fluid.

Numerical Investigation of Adiabatic Ice Slurry Flow through a Horizontal T–Shaped Pipe

Numerical Investigation of Adiabatic Ice Slurry Flow through a Horizontal T–Shaped Pipe

Multi-objective optimization of two-phase ice slurry flow and heat transfer characteristics in helically coiled tubes with RSM and NSGA-II

Ice slurry has been widely used in the field of building air conditioning because of its high energy storage density. The helically coiled tube heat exchangers (HCTHXs) utilizing ice slurry as the cooling medium presents a potential value in decreasing energy consumption for building air conditioning due to their high thermal efficiency. However, the design for HCTs utilizing ice slurry as the cooling medium is undeniably a challenging task due to its complicated structure and operation conditions. In this study, the response surface methodology (RSM) is utilized to construct the mathematical models, and the non-dominated sorting genetic algorithm (NSGA-II) is applied to optimize the thermo-fluidic behaviors of ice slurry in HCTs. Initially, five design parameters are determined, consisting of three operating parameters (inlet velocity (uin), inlet ice volume fraction (αin), ice particle diameter to tube diameter ratio (ds/D)) and two geometrical parameters (coil pitch to tube diameter ratio (H/D) and coil radius to tube radius ratios (Rc/r)). Next, numerical investigations are structured using the Box-Behnken design (BBD). Analysis of variance (ANOVA) is utilized to assess the validity and dependability of the generated regression models. To illustrate the interactions between each set of design parameters, response surface analysis is performed. In the end, the Pareto optimal frontier is determined using NSGA-II, in conjunction with the regression models generated through RSM. The obtained Pareto optimal solution resulted in a Nu of 223.5768 and a f of 0.029, representing improvements of 106.8 % and reductions of 28.86 % compared to the original design, respectively. The corresponding design variables is uin = 3.9974, αin = 29.3086 %, ds/D = 0.40408, H/D = 3.5908 and Rc/r = 22.6885. This study establishes a robust and effective groundwork for the advancement and utilization of HCTHXs utilizing ice slurry as the cooling medium.

Heat transfer in the melting of ice slurry during flow in a vertical slit channel

The article concerns the heat transfer process of ethanol ice slurry during downward and upward flow in a vertical slit channel (3x35.8x700mm) under constant heat flux density conditions. Experimental studies were conducted for three initial concentrations of ethanol (Xvai = 10.5 %, 13.2 %, 15.8 %) and mass fractions of ice of 0 ≤ xs ≤ 30 %. For upward flow, heat transfer coefficients were 6–14 % higher than for downward flow. For laminar flow, a greater effect of the melting process was observed, and for turbulent flow, the convection process had a greater effect on heat transfer coefficients. For laminar flow, the heat transfer coefficients of the ice slurry can be 200 % higher than the corresponding values for the carrier fluid. In turbulent flow, the corresponding increase in heat transfer coefficients did not exceed 15 %. For generalised non-Newtonian flow of ice slurry, criterion relationships were proposed for calculating heat transfer coefficients, taking into account the effect of the concentration of the carrier fluid, mass fractions of ice, its melting process, as well as the nature and direction of the flow.

Experimental investigation of ice slurry viscosity

This work attempted to conduct an experimental study which demonstrates the effect of the initial concentration of solute on the apparent viscosity of ice slurry in a horizontal circular pipe. The study was conducted on ice slurry based on propylene glycol, varying from 5 to 24% with different ice mass fractions varying from 5 to 25%. During the experiments, the initial concentration of the propylene glycol, ice concentration, and flow rate was modified as parameters. The flow tests were performed on laminar flows. The results of the investigation revealed that the ice slurry behaved like a non-Newtonian fluid, while it sometimes behaved like a Newtonian fluid. The rheological behavior of the ice slurry is reflected by its viscosity. For the shear-thickening behavior, the apparent viscosity increases with increasing the shear rate, and for the shear-thinning behavior, the viscosity decreases with increasing the shear rate, while for the Newtonian behavior, the viscosity remains almost constant. Then it was revealed that the viscosity of the mixture became too high for low shear rates at high ice mass fractions by increasing the concentration of the solute. The power law was used to establish a relationship between the apparent viscosity and the indexes of flow and consistency of ice slurry.

Study on flow and heat transfer characteristics of salt solution ice slurry

As a phase change material, ice slurry allows the storage of thermal energy in the form of latent heat. This has great advantages in terms of reducing energy consumption and environmental protection, and is being widely used. In this study, based on the Eulerian-Eulerian CFD model and the Population Balance Model (PBM), the flow and heat transfer characteristic of salt solution ice slurry was simulation studied, which included the pressure drop, friction coefficient, volume fraction, distribution of ice crystals and local heat transfer coefficient during the flow and solidification of salt solution ice slurry in different conditions. And the experimental system is set up to verify the results of the model and analyze the variation rules of these parameters. The results showed that in salt solutions with different concentrations, when the flow rate and solid phase volume fraction increase, the pressure drop and local heat transfer coefficient of the ice slurry will increase. The surface heat transfer coefficient reached to 2.5 × 103 W m-2 K-1, 2.9 × 103 W m-2 K-1, and 3.2 × 103 W m-2 K-1 when ice crystal volume fraction was 5 %, 10 %, and 15 %, respectively. The study will contribute to understanding of the changes in basic characteristics of salt solution slurry during the flow and phase transition processes.

On the stability of nanofluid ice slurry produced via impinging stream method under thermal and phase-change cycles

Nanofluid ice slurry has shown promising potential due to superior heat transfer and lower supercooling degree. The stability of the nanofluid ice slurry is of paramount importance to ensure high performance for practical applications. This study evaluates the stability (flow and thermal properties) of nanofluid ice slurry produced via a dynamic, impinging-stream method and compares with its conventional counterpart, i.e., the static, non-impinging-steam approach. Thermal cycling (heating–cooling) with phase change (freezing-thawing) cycles were carried out to measure absorbance, thermal conductivity, and viscosity. The results showed that when using the method of producing nanofluid ice slurry by impinging flow, nanofluid ice slurry with concentrations of 0.1, 0.2, and 0.3 w.t.% decreased in absorbance by 17%, 21%, and 26%, in thermal conductivity by 0.5%, 1.4%, and 2.17%, and in viscosity by 3.6%, 5.3%, and 10.4%, respectively, after nine freezing and thawing cycles. Additionally, for instance, for a nanofluid with a concentration of 0.2 w.t%, after 9 phase change cycles, the decrease in absorbance of the nanofluid solution using dynamic cycling was 7.1, 3.7, and 1.6 times higher than that of static cycling with an IPF of 25%, 50%, and 75%, respectively (thermal conductivity 4.1, 2.4, and 1.4 times; viscosity 2.8, 1.8, and 1.3 times). Higher nanoparticle concentration reduces the stability of the nanofluid ice slurry; the degree of reduction is first increased and then stabilized after six cycles. It was found that the dynamic method had an impact on the stability of the nanofluid compared with the static approach. Furthermore, empirical correlations were developed to predict the thermophysical properties based on phase-change cycles for practical applications.

Numerical study of ice slurry flow and heat transfer in successive U-bends as part of tubular heat exchangers

Using ice slurry can assist the energy saving in cooling systems. Ice slurries are used as secondary refrigerant in large cooling systems. They are mixtures of tiny ice particles in water and an antifreezing agent. The cooling can be stored in ice particles during off-peak conditions and released during peak condition. The stored cooling in ice slurry must be delivered to the desired system through a heat exchanger. Successive U-bend pipes commonly exist in tubular heat exchangers. However, this configuration has not been investigated yet for ice slurries. The present study aims to investigate the heat transfer of these mixtures in successive in-plane U-bends as part of heat exchangers. Mass transfer between ice slurry and fluid is the main important part of this problem which is considered in the present study. For the simulation of ice slurry, the Eulerian two-fluid numerical method is used along with the consideration of mass transfer between two phases and the kinetic theory of granular flow for ice particles viscosity. Nusselt number and pressure drops are mainly studied for different geometric configurations. The length between two bends are changed from 50 to 400 mm and the radius of curvatures of the bends are changed from 50 to 100 mm. The results of the study indicated that the average Nusselt number increases with the radius of curvature and distance between two U-bend pipes. Two successive U-bends neutralize each other's centrifigual effects, then ice particles have chances to rearrange and reduce the wall temperature in each bend. This effect is more prominent in higher distances between two bends and higher radii of curvature. At low radius of curvatures, the variation of distance between two bends has stronger effect on heat transfer of the system; in such a way that by doubling the distance between two bends, the Nusselt number increases 4.1% and 1.5% respectively for radius of curvatures 50 mm and 100 mm. Also it was shown that by increasing the radius of curvature and distance between two U-bend pipes the skin friction coefficient increases. It can be seen that by increasing the ratio of the distance between two bends to the radius, the performance evaluation criterion (PEC) increases.

Investigation on the evolution of ice particles and ice slurry flow characteristics during subcooling release

For the subcooling method ice slurry generator, the characteristics of ice slurry during subcooling release have a significant impact on the efficiency and stability of the system. An object of this paper is to investigate the evolution and distribution of ice particles in supercooled water and the flow characteristics of ice slurry during subcooling release in horizontal straight pipe, based on computational fluid dynamics (CFD). Moreover, the population balance model (PBM) is adopted to research the growth, agglomeration and breakage of ice particles. The effects of velocity, subcooling degree and ice volume fraction at the inlet are investigated. In terms of pressure and velocity, the average error between numerical simulations and experimental results is approximately 10%. The results indicated that the evolution of ice particle diameters is significantly affected by the degree of subcooling, which contribute to the growth of ice particles. For each 1 K increase in supercooling degree, the particle diameter will increase by 50 µm. The temperature trend of water from the supercooled state to the phase equilibrium state is consistent with the evolution of ice particles. Besides, the ice volume fraction along the vertical axis at the outlet can be divided into low-concentration, high-concentration, and stable regions, which is significantly affected by the degree of supercooling. Close to the wall, the ice volume fraction drops sharply due to collisions between the wall and the particles. The velocity of the ice slurry is symmetrically distributed along the vertical axis.

Numerical Study on Flow-Melt Characteristics of Ice Slurry in Horizontal Straight Pipe with a Local Large Heat Flux Segment

Ice slurry is a high energy density coolant with excellent flow, phase change, and thermophysical properties. In order to investigate the recovery of ice slurry flowing through a local large heat flux segment, a 3D Eulerian-Eulerian model based on the granular kinetic theory considering the flow and melting phase change of ice slurry is developed. Sensitivity analysis of interphase forces is carried out. A comparison of the pressure drop, solid phase velocity, and heat transfer coefficient with empirical data is carried out, respectively. The calculated results are in good agreement with the experimental results, indicating that the numerical model could accurately describe the flow and melting characteristics. Thermophysical field distributions, the axial variation of ice volume fraction (IVF), recovery curve, the average heat transfer coefficient, as well as the re-uniformization length are obtained. After passing through local large heat flux segment, due to shear stress action, the IVF and the particle uniformity of the cross section have recovery characteristics. The gradient of the recovery curve decreases with increasing inlet IVF as well as with increasing Reynolds number. After the local large heat flux increases to a certain value, its effect on the recovery curve of the ice slurry is small. The re-uniformization length increases as the local large heat flux increases. The average heat transfer coefficient of local large heat flux segment increases due to damage of the boundary layer. These results can provide a theoretical basis for the design of ice slurry systems in practical application.

Thermo-fluidic characteristics of ice slurry flows in U-bend pipes for cold thermal energy storage

Thermal energy storage plays an important role in improving the efficiency of refrigeration systems. Ice slurries have a high potential for thermal energy storage due to their high latent energy storage properties and almost uniform temperature field. Ice slurry flows in heat exchangers can assist in peak load conditions of refrigeration systems. In the present study, the thermo-hydraulic behavior of ice slurry in U-Bend pipes as a component of heat exchangers was investigated. Numerical simulations were perforfemd using multiphase two-fluid model. Kinetic theory of granular flows were used for modeling the viscosity of ice particles. The effect of geometry of U-Bend pipes on heat transfer rate, pressure drop and ice slurry phase change were investigated. Numerical results were in good agreement with the experimental data. The results showed that heat transfer coefficient and pressure drop increase with Reynolds number, ice volume fraction and ice particle diameter. Tripling the particle diameter leads to the Nusselt number increase by 76 %. It was also found that by reducing the radius ratio, the heat transfer coefficient and the average skin friction coefficient increase, but overally it improves the performance. With a 100 % increase in Reynolds number, the average Nusselt number increases by 80 %, and by decreasing the radius ratio to 50 %, the Nusselt number increases by <1 %.

Experimental investigation and modeling of the pressure drop of ice slurry flow in horizontal pipe

This study was conducted on ice slurry made by 11% of monopropylene glycol with various ice mass fractions through a horizontal pipe. The pressure drops, densities, temperatures, and ice slurry mass flow rates were measured and analyzed. First of all, the values of the pressure drop were validated with experimental results available in the literature. Then a numerical study of the flow of the ice slurry by pseudomonophasic flow model, which assumes the absence of the slip velocity between the phases and treats the ice slurry as a homogeneous and laminar fluid with thermophysical properties of the mixture. The rheological properties confirmed the non-Newtonian character of the ice slurry. The results show that there is a good agreement between the pressure drops of the present work and the literature. It was also found that the numerical analysis is very close to the experimental values in the case of a shear thinning flow.

Study of the convective heat transfer during full melt off of ice slurry in laminar and non-Newtonian flows

This paper presents the experimental results of the heat transfer coefficient of ice slurry in the distribution phase in order to conserve fish and shellfish where the ideal temperature oscillates between 0 °C and 2 °C. The required energy power absorbed during the exchange between the ice slurry and the air is assimilated to the transport capacity (in kW of cooling at full melt off). The secondary fluid was prepared by mixing monopropylene glycol, MPG, and water to obtain an initial concentration varying from 5 to 24% (the initially freezing temperature varying from − 1.84 °C to – 9.39 °C). The heat transfer coefficients for ice slurry in laminar flow conditions increased with velocity and ice concentration but decreased with increasing MPG concentration, according to the results. The heat transfer coefficients for ice slurry in laminar flow conditions increased with velocity and ice concentration but decreased with increasing MPG concentration, according to the results. The heat transfer coefficients of ice slurry are of the order of 7000 W.m−2.K−1.Moreover, the rheological behavior of the ice slurry greatly influenced the results under certain conditions. A new average Nusselt correlation was proposed that accurately predicts the superficial heat transfer coefficients of laminar flow of ice slurry through the horizontal pipe.

CFD modelling of the flow of ice slurry in a vertical slit channel

In this article, the Euler-Euler method was applied to CFD modelling of adiabatic ice slurry flow, for different flow directions in a vertical slit channel. The mean relative accuracy of determining pressure drops compared to experimental studies was 5.6%. Calculations showed that the relative slip velocity and the effect of flow direction on slip velocity increase with decreasing carrier fluid concentration, decreasing mean flow velocity, and decreasing mean solid particles volume fraction. The mean particle slip velocity does not exceed 4%, and local slip velocity values can be 58% of the mean suspended solids flow velocity. For heterogeneous flow, the highest slip velocities occur at a distance of 15% of the channel width from the channel sidewalls. The shape of the solid particles distribution profile is determined by the mean flow velocity and the mean solid particles volume fraction. Excluding the area at a distance of 8% of the channel width from the sidewall where local maximum (for low velocities) and minimum (for higher velocities) values may occur, the profile is stabilised in the central part of the channel. In this study, the boundary curves between heterogeneous and homogeneous flow were determined for ice slurry flow in a vertical slit channel.

Study on ice slurry flow characteristics based on genetic algorithm

Ice slurry is a solid-liquid phase fluid consisting of a liquid solution and ice particles. It is widely used in life and engineering because of its excellent cold-carrying capacity. In this paper, a genetic algorithm is used to optimize the ice slurry flow with the minimum pumping power as the objective function. The results show that the genetic algorithm can be effectively applied to the optimization of ice slurry flow characteristics within reasonable parameters. In addition, the transport characteristics of ice slurry are also analyzed. The selection of suitable ice mass fraction values under different working conditions can make the transport characteristics optimal.

Numerical investigation on ice slurry flow in horizontal elbow pipes

Ice slurry has been put into use as secondary refrigerant in many industrial fields due to its promising characteristics. But the complex flow properties of ice slurry flow have brought significant difficulties to transport processes. In this paper, a CFD-PBM coupled model has been employed to investigate the flow characteristics of the ice slurry flow in horizontal various elbow pipes. The ice kinetics processes (growth, aggregation, and breakage) are all taken into consideration. The results show that different elbow angles affect the pressure, velocity, ice size and uniformity of ice slurry when flowing across the elbow. Longer length and higher bending angle of elbow make boundary layer separation and secondary flow more obvious. For the elbow angle less than 90°, the redistribution of pressure and velocity enhance the aggregation process at pipe section center at elbow outlet sections, which results in the growth of ice particles. The inlet velocity, ice packing fraction (IPF) and elbow angle both influence the uniformity of ice slurry. Inlet velocity has positive correlation, while IPF and elbow angle have reverse effect. In order to improve the efficiency of ice slurry transport process and avoid the ice blockage, higher velocity, lower IPF and suitable elbow angle (less than 90°) are suggested.

Experimental study on a wet precooling system for fruit and vegetables with ice slurry

Aiming at the application of fruit and vegetables precooling, an innovative wet precooling system with ice slurry as a cooling medium was proposed. A small wet precooling room performance test platform was built. With apples as the precooling subject, the temperature and relative humidity in precooling room, the cooling rate and weight loss of apples as indexes, by changing the weight concentration of ice slurry additives (0%-8%), the ice fraction (0%-10%) and the ice slurry flow rate (50-150 L h−1), the precooling experiments were carried out. The results showed that increasing the concentration of ice slurry additives (NaCl) could effectively reduce the equilibrium temperature in precooling room. For the ice slurry solution with the additive concentrations of 0%, 2%, 4%, 6% and 8%, the equilibrium temperature in precooling room were 4.3°C, 1.7°C, 0.4°C, 0.0°C and -0.7°C, respectively. When the ice fractions increased from 0% to 10%, the precooling time decreased from 165 min to 96 min, and the weight loss decreased from 2.11% to 0.42%. When the ice slurry flow rate increased, the relative humidity in precooling room increased, and the cooling rate of apples firstly increased rapidly and then leveled off. When the flow rate reached 100 L h−1, the relative humidity remained above 90%. The precooling system has a strong applicability, easy to realize the stable environment of low temperature and high relative humidity (0°C, >90%), so it has a large application space in the precooling and fresh-keeping of fruit and vegetables.