Heat transfer studies on spiral plate heat exchanger

In this paper, the heat transfer coefficients in a spiral plate heat exchanger are investigated. The test section consists of a plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot water (hot fluid) is varying from 0.5 to 0.8 kg/s and the mass flow rate of cold water (cold fluid) varies from 0.4 to 0.7 kg/s. Experiments have been conducted by varying the mass flow rate, temperature, and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the Nusselt number which can be used for practical applications is proposed

Gas-inducing-type mechanically agitated contactors: hydrodynamic characteristics of multiple impellers

The rate of gas induction was measured in gas-inducing-type mechanically agitated contactors (GIMAC) provided with two impellers. Three vessels of 0.57, 1.0, and 1.5 m i.d. were used. Tap water was used as the liquid phase, and air was used as the gas phase. Six different impeller designs (pitched-blade downflow and upflow turbines straight-blade turbine, disk turbine, and upflow and downflow propellers) were employed. From these designs, six different impeller combinations were made and an optimum combination has been proposed. The impeller speed was varied in the range of 0.30 to 15.45 rev/s. The ratio of impeller diameter to tank diameter (D/T) and the submergence (S) of upper impeller from the top were varied. The effects of clearance of lower impeller from the tank bottom (C1) and the impeller spacing (C3, distance between the two impellers) were also varied over a wide range. The design of the lower impeller was optimized in terms of diameter (D), blade width (W), blade angle (BΦ), number of blades (nb), and the blade thickness (tb). Rational correlations have been developed for the critical impeller speed for gas induction and the rate of gas induction

Gas inducing type mechanically agitated contactors

The rate of gas induction was measured in 0.57, 1.0, and 1.5 m i.d. gas inducing types of mechanically agitated contactors (GIMAC). The ratio of impeller diameter to vessel diameter was varied in the range 0.13 < D/T < 0.59. The effect of impeller submergence from the top and impeller clearance from the bottom was investigated in detail. The effect of impeller speed was studied in the range 0.13 < N < 13.5 r/s. A model has been developed for the critical speed for gas induction, and for the rate of gas induction with the description of forced vortex structure in the impeller region. A unified theme has been proposed for the understanding of phenomena such as the critical speed for gas induction and the rate of gas induction. The physical significance of model parameters has been interpreted on the basis of flow information in the impeller region

Power consumption in gas-inducing-type mechanically agitated contactors

Power consumption was measured in 0.57, 1.0, and 1.5 m i.d. gas inducing type of mechanically agitated contactors (GIMAC) using single and multiple impellers. The ratio of impeller diameter to vessel diameter was varied in the range of 0.13 < D/T < 0.59. The effect of liquid submergence from the top and impeller clearance from the vessel bottom was investigated in detail. In the case of multiple impeller systems, six different designs were investigated. The designs included pitched blade downflow turbine (PBTD), pitched blade upflow turbine (PBTU), downflow propeller (PD), upflow propeller (PU), straight bladed turbine (SBT) and disc turbine (DT). The effect of interimpeller clearance was studied for the multiple impeller system. The effect of impeller speed was studied in the range of 0.13 < N < 13.5 rotations/s. A mathematical model has been developed for power consumption before and after the onset of gas induction