Numerical solutions for skin tissue temperature during scald injury events are obtained and utilized in conjunction with a thermal injury criterion, to predict critical exposure levels for various heated fluids. A one-dimensional tissue model of the type used by Love is employed to determine the initial tissue temperature distribution. The bio-heat equation for tissue heat transfer is then solved via an implicit finite difference technique, subject to convective heating and cooling at the surface. The sensitivity of the critical exposure level to variations in tissue properties and convective heating coefficients is investigated. Thermal injury thresholds are presented for various fluids along with bounds to reflect uncertainty in assumed tissue properties. The results obtained are in good agreement with existing experimental scald injury data. iii PREFACE This report is a product of a short term research effort sponsored by the National Bureau of Standards, Center for Consumer Product Technology (CCPT). The objective of this research is a more thorough understanding of thermal injury from heated fluidsa prerequisite for the development of improved product standards. The work reported herein, dealing with the heat transfer aspects of thermal injury, was performed in the Product Performance Engineering Division of CCPT. Companion work in the area of thermal injury criteria was conducted concurrently in the Product Safety Division of CCPT, and provided the basis for quantifying thermal injury in the present study. iv
As annual operating efficiency of vented heating equipment is affected by burner fuel and combustion air modulation, it is important to differentiate between the various types of controls in determining annual energy requirements. Test procedures for evaluating annual efficiency have already been developed and implemented by the Department of Energy (DoE) for furnaces with single-stage thermostat control. A modified test procedure is necessary to account for operation with fuel modulation. A revised procedure which accommodates two types of fuel modulating controls has recently been developed. Tests are conducted at reduced and maximum firing rates, and along with typical derived values, from a bin analysis of weather data, the fraction of the total hours for each operating mode is obtained to calculate a weighted annual efficiency. These test methods and calculation procedures are based on and are an extension to the current DoE test procedures for the single-stage type of thermostat control of central warm air furnaces.By using the procedures developed in the report, the energy savings impact of fuel modulating controls when combined with the use of modulated combustion air is evaluated. Energy savings from 6 percent to 20 percent were determined from the increase in efficiency with both fuel and combustion air modulation. Improved efficiency was dependent on the type of thermostat control and the minimum-to-maximum fueled input; i.e., turndown ratio.
A study of the human factors aspects of five selected items of Navy equipnent, namely, oxygen breathing apparatus, safety harness, emergency escape scuttle, life rails, and rotary observation windows, has been undertaken to ensure that the smaller size and lesser strength of females would not be a deterrent to the use of the equipment by women . The study involved a review of the applicable specifications for each item of equipment, a survey and erameration of male and female anthropcmetric data, and a linking of engineering and anthropcmetric data. Each item has been assigned to a hazard category.
A study has been undertaken to quantify appliance water consumption and the effectiveness of various consumer usage techniques and manufacturer design modifications for saving water. Appliances considered are clothes washers and dishwashers. Through a comparison of estimated water savings, the study indicates that the most significant means of saving water are those which are already commercially availablefront-loading machines and suds-saver options for clothes washers, and short-cycle setting? for dishwashers. Water savings ot about 20 to 30 percent are estimated with these features, or about 10 ga_lons for clothes washers and 3 gallons for dishwashers.Several appliance design modifications are also evaluated but do not offer the same level of savings. Water usage characteristics such as supply and discharge flow rates and the effect of supply pressure and cycle selection are presented.
The effects of various energy-conserving modifications on water heating energy consumption were evaluated based on laboratory tests. Nine storage-type residential water heaters, representative of standard and "energy-saving" electric, gas, and oil fueled models currently on the market, were obtained for testing. Federally-promulgated water heater test procedures were used to measure the energy consumption of each unit before and after modifications. Energy-conserving modifications and corresponding projected reductions in energy consumption included: reduced thermostat settings (10°C), 12 percent savings for standard electric, gas, and oil fueled water heaters (where appliance performance does not degrade below an acceptable level, and water heater capacity is still sufficient to meet hot water needs); and improved insulation, 9 percent savings for all water heater fuel types. Also considered for gas-fired units were reduced pilot input rate from 220 W to 60 W (750 Btu/h to 200 Btu/h), less than 2 percent savings; use of thermal dampers, 3 percent savings; use o£ intermittent ignition, 5 percent savings; and use of intermittent ignition and mechanical flue dampers, 11 to 16 percent savings. Modifications to energy-saving models resulted in somewhat smaller reductions. Multiple modifications were found to offer energy savings slightly less than the sum of the individual savings.
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