Abstract

Effluent streams from the Modular Caustic-Side Solvent Extraction Unit (MCU) will transfer to the tank farms and to the Defense Waste Processing Facility (DWPF). These streams will contain entrained solvent. A significant portion of the Strip Effluent (SE) pipeline (i.e., acid stream containing Isopar{reg_sign} L residues) length is within one inch of a sludge stream. Personnel envisioned the sludge stream temperature may reach 100 C during operation. The nearby SE stream may receive heat from the sludge stream and reach temperatures that may lead to flammability issues once the contents of the SE stream discharge into a larger reservoir. To this end, personnel used correlations from the literature to estimate the maximum temperature rise the SE stream may experience if the nearby sludge stream reaches boiling temperature. Several calculation methods were used to determine the temperature rise of the SE stream. One method considered a heat balance equation under steady state that employed correlation functions to estimate heat transfer rate. This method showed the maximum temperature of the acid stream (SE) may exceed 45 C when the nearby sludge stream is 80 C or higher. A second method used an effectiveness calculation used to predict the heat transfer rate in more » single pass heat exchanger. By envisioning the acid and sludge pipes as a parallel flow pipe-to-pipe heat exchanger, this method provides a conservative estimation of the maximum temperature rise. Assuming the contact area (i.e., the area over which the heat transfer occurs) is the whole pipe area, the results found by this method nearly matched the results found with the previous calculation method. It is recommended that the sludge stream be maintained below 80 C to minimize a flammable vapor hazard from occurring. « le Document type: Report

Abstract

A preliminary study of the feasibility of using existing drinking water supply systems to provide hot water for heating purposes to a typical 140-home subdivision has been undertaken. This preliminary study has centered on (i) types of municipal water system designs and effects of system design upon heating use; (ii) methods of using low-to-moderate temperature water for heating purposes and possible institutional barriers; (iii) identification and description of a typical residential community suitable for hot water heating; (iv) evaluation of thermal losses in the uninsulated main distribution system from the main pumping station having assumed geothermal heating to the subdivision; (v) evaluation of thermal losses in the uninsulated street mains in the subdivision; (vi) estimation of size and cost of the pumping station main heat exchanger to supply geothermal energy to the drinking water; (vii) sizing of individual house heat exchangers; (viii) pumping and power requirements to supply the increased water flow rate through the subdivision street water distribution lines; and (ix) pumping and piping requirements to provide heating water flow from the street lines to a typical residence. From the results obtained thus far, it would appear that the use of existing uninsulated water supply systems will be advantageous more » in many communities having nearby low-to-moderate temperature geothermal resources. « le Document type: Report

Abstract

We design heat exchangers using two topology optimization approaches: the density, i.e. volume fraction and level set methods. Our goal is to maximize the heat exchange between two fluids in separate channels while constraining the pressure drop across each channel. The heat exchanger is modeled with a coupled thermal-flow formulation. The flow is governed by an isothermal and incompressible Stokes-Brinkman equation and the heat transfer is governed by a convection-diffusion equation with high Peclet number. We solve one set of Stokes-Brinkman equations per fluid. Each Brinkman term in the flow equation serves to model the other phase as a solid, thereby preventing mixing. We first represent the solid and fluid phases using a volume fraction variable and apply a SIMP-like penalization in the Brinkman term to drive the optimization to a discrete design. The cost and constraint function derivatives are automatically calculated with the library pyadjoint and the optimization is performed by the Method of Moving Asymptotes. In a second optimization formulation, we use the level set approach to define the interface that separates the two fluids. Pyadjoint calculates the shape derivatives of the cost and constraint functions and the Hamilton-Jacobi advects the interface, allowing for topological changes. We present results in two dimensions and discuss the advantages and disadvantages of each approach.