Two-Phase Flow of Two HFC Refrigerant Mixtures Through Short Tube Orifices, Draft Final Report

The need for new refrigerants was established when scientists first realized the ozone depleting effects of CFC and HCFC refrigerants. The chlorine atom in these refrigerants is capable of reaching the upper atmosphere where one chlorine atom can destroy more than 100,000 ozone atoms(Lang1ey 1994). Laws have been enacted to halt the destruction of the ozone layer and force industry to find replacements for the ozone depleting refrigerants. Section 608 of the Clean Air Act (1990) prohibited the venting of ozone depleting refrigerants as of July 1, 1992. In addition the Clean Air Act (1990) also requires the EPA to develop regulations limiting the emissions of ozone depleting refrigerants. Efforts are currently underway to find CFC replacements before the complete phaseout of CFC manufacturing in January of 1996. Much of the effort to replace CFC and HCFC refrigerants has centered on development of refrigerant mixtures that could replace R-22. Before systems can be designed with a new refrigerant (or mixture), thermodynamic and thermophysical properties must first be characterized. An important component in air conditioners is the expansion device. Because of their low cost, several manufacturers have chosen to use short tube orifices for the expansion device in their systems. Designing a system with an orifice requires knowledge of the flow characteristics of short tube orifices. Recent work on orifices has focused on R-12 and R-22 (Kim and O'Neal, 1993a; Aaron and Domanski, 1990; Krakow, 1988; and Mei, 1982). In addition, there are unpublished data on R-134a @m and ONeal, 1993b) and the effect of lubricants on flow characteristics (Kim, 1993; Kim and O'Neal, 1994b).The present study presents data for flow of two refrigerant mixtures through short tube orifices. The two mixtures were R3211251134a (23%/25%/52% on a mass percentage basis) and R321125 (50%/50%). The following presents results for the flow of these two refrigerants through short tube orifices of various diameters and lengths of 0.5 in (12.7 mm), 0.75 in (19.05 mm), and 1.00 in (25.4 mm) in a pure form and mixed with various mass percentages of oil

PROFITABILITY ANALYSIS OF SOYBEAN APHID CONTROL TREATMENTS IN THREE NORTH-CENTRAL STATES

Crop Production/Industries,

The Use of Preconditioned Iterative Linear Solvers in Interior-Point Methods and Related Topics

Over the last 25 years, interior-point methods (IPMs) have emerged as a viable class of algorithms for solving various forms of conic optimization problems. Most IPMs use a modified Newton method to determine the search direction at each iteration. The system of equations corresponding to the modified Newton system can often be reduced to the so-called normal equation, a system of equations whose matrix ADA' is positive definite, yet often ill-conditioned. In this thesis, we first investigate the theoretical properties of the maximum weight basis (MWB) preconditioner, and show that when applied to a matrix of the form ADA', where D is positive definite and diagonal, the MWB preconditioner yields a preconditioned matrix whose condition number is uniformly bounded by a constant depending only on A. Next, we incorporate the results regarding the MWB preconditioner into infeasible, long-step, primal-dual, path-following algorithms for linear programming (LP) and convex quadratic programming (CQP). In both LP and CQP, we show that the number of iterative solver iterations of the algorithms can be uniformly bounded by n and a condition number of A, while the algorithmic iterations of the IPMs can be polynomially bounded by n and the logarithm of the desired accuracy. We also expand the scope of the LP and CQP algorithms to incorporate a family of preconditioners, of which MWB is a member, to determine an approximate solution to the normal equation. For the remainder of the thesis, we develop a new preconditioning strategy for solving systems of equations whose associated matrix is positive definite but ill-conditioned. Our so-called adaptive preconditioning strategy allows one to change the preconditioner during the course of the conjugate gradient (CG) algorithm by post-multiplying the current preconditioner by a simple matrix, consisting of the identity matrix plus a rank-one update. Our resulting algorithm, the Adaptive Preconditioned CG (APCG) algorithm, is shown to have polynomial convergence properties. Numerical tests are conducted to compare a variant of the APCG algorithm with the CG algorithm on various matrices.Ph.D.Committee Chair: Monteiro, Renato; Committee Member: Green, William; Committee Member: Nemirovski, Arkadi; Committee Member: Parker, R. Gary; Committee Member: Shapiro, Alexande

Trends in Building Energy Usage in Texas State Agencies

In late 1983, a cost containment program was initiated out of the governor's office directed at the major state agencies. The Energy Management Group at Texas A&M University provided technical expertise in obtaining agency energy usage and cost figures for the fiscal years 1981 to 1983. While there is considerable diversity from agency to agency, the trend is toward dramatically higher energy cost per square foot for virtually all agencies. This alarming trend can be partially explained by rising unit costs for gas and electricity and a lack of incentives for conservation efforts due to the method of utility budget allocations. A building standard signed into law in 1976 could have reduced energy consumption, but was never enforced. Beginning in fiscal year 1986, universities will be allowed to comingle utility money with capital operating money so that conservation can really pay off for them

Economic Evaluation of Insulation/Radiant Barrier Systems for the State of Texas

This paper presents simulated performance of insulation/radiant barrier systems under different Texas climates. A transient heat and mass transfer model which predicts thermal performance of residential attics (Medina, 1992) was coupled with an "economic" subroutine. Simple payback periods were estimated which were based on current insulation and radiant barrier (RB) prices (materials and installation), and current and forecast electric rates. It was found that when the analyses were based solely on reductions of ceiling heat loads during the summer time, a combination of R-11 with RB was more effective than upgrading the insulation level to R-19. Similarly, adding a radiant barrier to an existing insulation level of R-19 proved more effective than upgrading to R-30. When heat gains to the cold air traveling inside A/C ducts (\which are usually installed in attic spaces) were considered, all insulation/radiant barrier combinations showed faster payback periods than insulation upgrades, During the winter time, insulation upgrades proved to be more effective than insulation/radiant barrier combinations. The simple payback analyses presented herein include both summer and winter simulations

The Impact of Endothall on the Aquatic Plant Community of Kress Lake, Washington

CA dense mat-forming population of Eurasian watermilfoil ( Myriophyllum spicatum L . ) was interfering with fishing and recreation in a small western Washington lake. A low concentration (1.5 mg/L active ingredient) of the herbicide endothall formulated as Aquathol® K was used in 2000 to attempt to selectively control the Eurasian watermilfoil. Aquatic plant biomass and frequency data were collected before treatment, ten weeks after treatment and during the growing season for 3 additional years. Macrophyte data were analyzed to assess the herbicide’s impacts on Eurasian watermilfoil as well as the rest of the aquatic plant community. Results showed a significant decrease in Eurasian watermilfoil biomass and frequency 10 weeks after treatment. The Eurasian watermilfoil continued to be present, but at a significantly reduced level through the remainder of the study (3 years after treatment). Of the native plant species, large-leaf pondweed ( Potamogeton amplifolius Tucker . ) frequency and biomass was significantly reduced after treatment. Common elodea ( Elodea canadensis Rich.), muskgrass ( Chara sp. Vallaint.) and bladderwort ( Utricularia sp. L.) all increased significantly after treatment. (PDF has 6 pages.

Metering and Calibration in LoanSTAR Buildings

End-use metering in commercial buildings often requires installation of a large variety of transducers and data loggers. The metering installation group in the LoanSTAR monitoring program has the primary responsibility for the installation and maintenance of the metering hardware. This paper provides an overview of the responsibilities and first year experiences of the metering installation group of the LoanSTAR monitoring program. In addition, the calibration laboratory is also described

Racial Differences in Survival among Hemodialysis Patients after Coronary Artery Bypass Grafting

The aim of this study was to examine racial differences in long-term survival among hemodialysis patients after coronary artery bypass grafting (CABG). To our knowledge this has not been previously addressed in the literature. Black and white hemodialysis patients undergoing first-time, isolated CABG procedures between 1992 and 2011 were compared. Survival probabilities were computed using the Kaplan-Meier product-limit method and stratified by race. Hazard ratios (HR) and 95% confidence intervals (CI) were computed using a Cox regression model. A total of 207 (2%) patients were on hemodialysis at the time of CABG. White (n = 80) hemodialysis patients had significantly decreased 5-year survival compared with black (n = 127) patients (adjusted HR = 1.9, 95% CI = 1.2–2.8). Our finding provides useful outcome information for surgeons, primary care providers, and their patients

An Analysis of Efficiency Improvements in Residential Sized Heat Pumps, Final Report, May 1986

The objectives of this study included: (1) development of classes of heat pumps, (2) evaluation and selection of a suitable heat pump design model, (3) characterization of suitable baseline heat pump designs, (4) selection of design options that can be used to improve heat pump efficiency, and (5) development of heat pump designs to cover the whole spectrum of efficiencies available today and those that may be technologically feasible in the next few years