Pratihar, A.K.Rawat, Kamal Singh2019-02-042019-02-042018-01http://krishikosh.egranth.ac.in/handle/1/5810093522The use of ice slurry as a working fluid in secondary-loop of refrigeration system not only enhances the system performance but also reduces the refrigerant charge and its leakage to environment. Thus, presents exciting solution of the two pronged problem of energy and environment safety. Ice slurry can be transported through pipes, however, ice slurry flow is a complex solid-liquid two phase flow, which significantly differs from the single phase flow. During the ice slurry flow in horizontal pipe, the ice particles tend to float (due to density difference) towards the top of the pipe and different ice concentrations exist in the radial direction of the pipe. Depending on ice concentration distribution, the flow can be classified into four flow categories viz. homogeneous, heterogeneous, moving bed and stationary bed flow. The flow of ice slurry depends on various operating parameter viz. initial velocity, ice concentration, freezing point depressant concentration and particle size. As the flow of ice slurry through a pipe is a complex S-L flow, it is a formidable task to analyze this type of flow experimentally due to complexities in measurements and visualization. Therefore, a CFD model is developed to simulate the ice slurry flow in various flow regimes through various pipe geometries. In the modeling of ice slurry flow, various interfacial forces viz. drag force, lift force and turbulence dispersion forces are considered. The turbulence in the ice slurry flow is modeled by the per phase k-model. The CFD model has been first validated with the experiment results of the ice and sand-water slurry flow in various pipe geometries. After validation of the present model, the simulation of ice slurry flow has been carried out in four type of pipes; horizontal pipe, vertical pipe, 90o elbow bend pipe and 180o U-bend pipe. Simulation has been carried out to predict the critical velocity and the effect of different parameters on critical velocity in a horizontal pipe. For transportation of ice slurry, homogeneous and heterogeneous flow regimes are recommended therefore, investigation of ice slurry flow in these regimes has been carried out in different pipes to study the effect of different parameters. Apart from that, the effect of different bend radius ratios (R/r) on the ice slurry flow has also been investigated in bend pipes. The critical velocity is significantly influenced by the particle size. Critical velocity at 10% initial ice concentration increases from 0.4 m/s to 0.16 m/s with increase in particle size from 0.1 mm to 0.4 mm. The pressure drop for the heterogeneous slurry flow in both horizontal and vertical pipes increases with increase in initial velocity and ice concentration due to increase in the rate of interaction between solid-liquid and number of collisions among the particles and with wall increase which causing more frictional losses. Beside this, in vertical pipe pressure drop in case of downward flow is upto 12 % more in comparison to that in upward flow due to turbulence losses. In the ice slurry flow through bend pipes, centrifugal force acts on the fluid which results in secondary flow at the bend section similar to single phase flow. The value of pressure drop, velocity and particle distribution in the bend section is significantly affected by the secondary flow. However, the effect of secondary flow becomes less predominant at higher bend radius ratios.ennullThesis