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In this study, a mathematical model was developed for falling film evaporation in vacuum using heat transfer relations. An experimental device was designed. experimental set-up which was used was equipped with a triangular weir distribution device and it had the ability to record data up to 3 m. Experiments were performed in a single-effect process with sucrose-water solution varying from 3 to 20% concentration rate of sucrose and we used a vertical tube evaporator with the dimensions of laboratory scale. The model that was developed considers convection, shear stress, viscosity and conjugate heat transfer while most of the previous works ignored these factors. The main factors influencing the heat transfer mechanism performance of the unit were investigated and analyzed. We concluded that the experimental studies are verified by the developed model. Furthermore, it was also concluded that, the heat transfer is affected by the mass flow rate, sucrose concentration rate in solution, film thickness and pressure. List of symbolsA Area (m 2 ) c Concentration (kg/kg) d Thickness, diameter (m) f Interfacial friction factor g Gravity (m/s 2 ) h Heat transfer coefficient (W/m 2 K) h High (m) i Enthalpy (kJ/kg) k Heat transfer coefficient (W/m K) Ka Kapitza number l Characteristic length (m) _ m Mass flow rate (kg/s) Nu Nusselt number Pe Peclet number Pr Prandtl number q Heat flux (W/m 2 ) Q Heat (W) Re Reynolds number t Time (s) T Temperature (°C) U Overall heat transfer coefficient (W/m 2 K) V Velocity, liquid film velocity (m/s) _ V Volumetric rate (m 3 /s) W Length (m)Greek letters l Dynamic viscosity (Pa s) m Kinematic viscosity (m 2 /s) s Shear stress (N/m 2 ) q Density (kg/m 3 ) d Film thickness (m) a Heat transfer coefficient (W/m 2 K) k Heat transfer coefficient (W/m K)

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The total force produced in the axial direction on a pump is called axial load and is caused by the pressure difference between the front and rear of the impeller and the hydrostatic force in the suction direction. In a centrifugal pump, 3D computer-aided analysis programs are used to design and reduce R&D and manufacturing costs. In this study, parameters affecting axial load of the centrifugal pump with a single suction and closed impeller were investigated by using the Computational Fluid Dynamics (CFD) method. In this context, the flow rate and the some physical properties such as the back gap of the impeller, wear ring and balancing holes, of the centrifugal pump were investigated to determine how much affected the axial load. The results showed that the wear ring and the balancing holes give rise to effective results on the axial load, while the back gap of the impeller does not affect the large extent. With the design changes made with these parameterizations, the axial force was reduced by up to 60%, whereas the efficiency was decreased by 5%. The loss of efficiency due to this decrease in axial force is negligible. However, higher efficiency values were also found at a different point from the working point where the axial load is lowest.