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Fully developed axial laminar flow of viscoplastic Herschel-Bulkley fluids in eccentric annuli between two pipes has been investigated numerically. The pipes are closed at one end and flow is due to the axial motion of the inner pipe. The annuli may be filly open or partially blocked. General non-orthogonal, boundary-fitted curvilinear coordinates have been used to accurately model the irregular annular geometry due to the presence of a flow blockage. A computer code has been developed using a second-order finite-difference scheme. An exponential model for the shear stress, valid for both yielded and unyielded regions of the flow, is used in the computation. The effects of generalized Bingham number, flow behavior index, eccentricity, and blockage height on the pressure gradient or the surge pressure have been studied and the results are presented in dimensionless form. The pressure gradient is found to decrease with increasing eccentricity. For a partially blocked eccentric annulus the pressure gradient is found to decrease with an increase in the blockage height. ~~On a etudie numeriquement l'ecoulement laminaire axial completement developpe de fluides viscoplastiques d'Herschel-Bulkley dans des espaces annulaires eccentriques entre deux conduits. Les conduits sont fermes a une extremite et l'ecoulement est dii au deplacement axial du conduit interieur. L'espace annulaire peut &re entierement ouvert ou partiellement bloque. On a utilise des coordonntkes curvilineaires general, adaptkes au contour et non orthogonales, afin de modtliser avec precision la geometrie annualire irreguliere due a la presence d'un blocage de I'ecoulement. Un programme de calcul base sur un schema de differences finies du second ordre a ete mis au point. On utilise dans le calcul un modele exponentiel pour la contrainte de cisaillement, qui est valable autant pour la region cisaillee que non cisaillee. Les effets du nombre de Bingham generalise, de I'indice de comportement de l'ecoulement, de I'eccentricite et de la hauteur du blocage sur le gradient de pression ou la surpression ont ete etudies et les resultats sont presentes sous forme adimensionnelle. On a trouve que le gradient de pression diminuait avec I'augmentation de I'eccentricite. Pour un espace annulaire eccentrique partiellement bloque, on a trouve que le gradient de pression diminuait avec une augmentation de la hauteur de bloquage.

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Fully developed laminar axial flow of yield-power-law fluids in eccentric annuli has been investigated numerically. The annuli may be fully open or partially blocked. General nonorthogonal, boundary-fitted curvilinear coordinates have been used to accurately model the irregular annular geometry due to the presence of a flow blockage. A computer code has been developed using a second-order finite-difference scheme. An exponential model for the shear stress, valid for both yielded and un-yielded regions of the flow, is used in the computation. The effects of pressure gradient, eccentricity, and blockage height on the flow rate have been studied and the results are presented. The flow rate is found to increase with increasing eccentricity for eccentric annuli without any blockage. For partially blocked eccentric annuli, the flow rate at a particular eccentricity decreases as the blockage height is increased.

The Rankine cycle is used commercially to generate power in stationary power plants using water as the working fluid. For waste heat recovery applications, where the temperature is lower, water is typically replaced by a carefully selected organic fluid. This work is based on using the waste heat in an automobile to generate electricity using the Organic Rankine cycle (ORC) with R245fa (1, 1, 1, 3, 3 penta-fluoropropane) as the working fluid. The electricity thus generated can be used to drive the accessory load or charge the battery which in any case helps improve the fuel economy. A simple transient numerical model has been developed that is capable of capturing the main effects of this cycle. Results show that exhaust heat alone can generate enough electricity that is capable of bringing about an improvement to the fuel economy under transient drive cycle conditions. Power output during EPA Highway drive cycle is much higher than EPA City due to higher exhaust mass flow rate and temperature. Time needed to reach operating conditions or in other words, the warm-up time plays an important role in the overall drive cycle output. Performance is found to improve significantly when coolant waste heat is used in conjunction with the residual exhaust heat to pre-heat the liquid. A sizing study is also performed to keep the cost, weight, and packaging requirement down without sacrificing too much power. With careful selection of heat exchanger design parameters, it has been demonstrated that the backpressure on the engine can be actually lowered by cooling off the exhaust gas. This lower backpressure will further boost the fuel economy gained by the electricity produced by the Rankine bottoming cycle.