Analysis of heat transfer in a vessel with helical pipe coil and multistage impeller

Abstract

Results of heat transfer coefficient measurements in an agitated vessel heated or cooled by the liquid media flowing in a helical pipe coil are presented in this paper. The multistage impeller made of two pitched six-blade impellers and adjustable clearance was used in a vessel with conical bottom. The transient method based on measuring the temperature dependency on time and solving the unsteady enthalpy balance was used to determine the heat transfer coefficients between the agitated liquid and the helical pipe coil. The results are summarized by the Nusselt number correlations, which describe the dependency on the impeller Reynolds number. The second part of this paper introduces a theoretical analysis of the flow in the liquid batch near the helical pipe coil. Based on the known pumping capacity of the multistage impeller, the characteristic velocity near the helical pipe coil can be evaluated. This characteristic velocity can be then used to determine the Nusselt number describing the heat transfer in a flow around a cylinder with the same cross-section profile as the helical pipe coil. A clear correlation between this Nusselt number and the integral Nusselt number is presented in this paper and introduces an alternative approach for prediction of heat transfer characteristics on the basis of hydrodynamic parameters describing an agitated system.

Application of the Temperature Oscillation Method in Heat Transfer Measurements at the Wall of an Agitated Vessel

“…Local values of the Nusselt numbers can be calculated according to (2), and it is possible to express the mean Nusselt number dependency by a commonly used correlation (18).…”

“…One possibility is using thin film heat flux sensors, which measure small temperature differences arising from the heat flow rate through a thin film element made of material with known properties. Transient methods determine the heat flow rate, for example, on the basis of a monitored temperature profile of the liquid accumulating the supplied heat, see [1,2] for a description of this approach.…”

“…Parameters m, n, and C in correlation (4) for various cases in the literature. L char represents the characteristic length in equation (2). Subscript 0 refers to the stagnant point in the impinging jet.…”

An Investigation of the Heat Transfer Performance of Dual Improved Intermig Impellers in a Stirred Tank With an Inner Heating Coil

“…As the heating fluid mass flow is fixed at 0.0333kg/s and the Reynolds number for this flow rate based on the inside diameter of the heating coil is around 8000, the empirical equation 12is used for calculating the inside coil heat transfer coefficient (Dostál et al, 2014).…”

“…What is more, the heat transfer performance of doubleshaft mixing is much better than that of single-shaft mixing. In addition, Dostál et al (2014) adopted the transient method based on measuring the temperature dependency on time and solving the unsteady enthalpy balance to determine the heat transfer coefficient between the agitated liquid and the helical pipe coil. Delgado et al (2017) conducted experimental studies on the heat transfer process in a stirred tank with internal heating coils using a phase change material (PCM) emulsion as a thermal energy storage system and determined the heat transfer coefficient between the spiral internal heating coils and the PCM emulsion.…”