The effect and contribution of wind generated rotation on outlet temperature and heat gain of LS-2 parabolic trough solar collector

The Monte Carlo ray tracing method is applied and coupled with finite volume numerical methods to study effect of rotation on outlet temperature and heat gain of LS-2 parabolic trough concentrator (PTC). Based on effect of sunshape, curve of mirror and use of MCRT, heat flux distribution around of inner wall of evacuated tube is calculated. After calculation of heat flux, the geometry of LS-2 Luz collector is created and finite volume method is applied to simulate. The obtained results are compared with Dudley et al test results for irrotational cases to validate these numerical solving models. Consider that, for rotational models ,the solving method separately with K.S. Ball's results. In this work, according to the structure of mentioned collector, we use plug as a flow restriction. In the rotational case studies, the inner wall rotates with different angular speeds. We compare results of rotational collector with irrotational. Also for these two main states, the location of plug changed then outlet temperature and heat gain of collector are studied. The results show that rotation have positive role on heat transfer processing and the rotational plug in bottom half of tube have better effectual than upper half of tube. Also the contribution of rotation is calculated in the all of case studies. Working fluid of these study is one of the oil derivatives namely Syltherm-800. The power of wind can be used to rotate tube of collector

The effect of geometrical characteristics of wavy strip turbulator and thermodynamic properties of fluid on exergy loss and heat transfer in a tube in tube heat exchanger

The present work conducts an experimental investigation into the influence of flow, thermodynamic and geometrical characteristics of the wavy strip on exergy loss and dimensionless exergy loss in a tube in tube heat exchanger. The working fluid is water with hot water passing the inner tube and cold water passing annulus. Wavy strips with four different angles and three widths were investigated experimentally. The result of exergy loss and dimensionless exergy loss for various conditions is presented and on the basis of curve fitting, three empirical correlations are suggested to predict dimensionless exergy loss in a double tube heat exchanger.https://www.tandfonline.com/loi/ueht202019-10-02hj2019Mechanical and Aeronautical Engineerin

THERMAL ANALYZING OF DISC TYPE WINDINGS WITH DIRECTED OIL FLOW

ABSTRACT In this paper, a model of a disc type winding for a transformer with directed oil flow is presented which utilizes a network of oil flow paths. Along each path segment, oil velocities and temperature rises are computed. The model includes temperature dependent oil density, resistivity, and oil viscosity and temperature and velocity dependent heat transfer and friction coefficients. Because of the non-linearity, an iterative solution is necessary. Temperature and oil velocities are computed and compared with experiment values. From this, the average winding temperature rise and the hot spot temperature can be determined. The model assumes the oil flows in definite paths and ignores local circulation, since we assume the oil flow is guided by means of oil flow washers, this assumption should be fairly accurate. The disc type winding is assumed to be subdivided into directed oil flow cooling paths

Study the effect of axially perforated twisted tapes on the thermal performance enhancement factor of a double tube heat exchanger

The main objective of this numerical study is to investigate the ways to reduce the pressure drop and consequently increase thermal performance enhancement factor (TEF) of a heat exchanger equipped with twisted tapes. For this purpose, axial perforated twisted tapes (PTTs) with various hole diameters are used instead of simple twisted tapes (STTs). Moreover, the variations of the effectiveness with number of transfer units (NTU) for different heat capacity ratios (Cr) were presented. The numerical model was well validated with the available experimental results. The results indicated that the use of perforated twisted tape leads to a reduction in pressure drop and heat transfer rate, subsequently; a significant increase in TEF was seen compared to simple twisted tapes. In addition, some correlations were formulated to present the numerical results