Greg Schoenau

Gasification of refuse derived fuel in a fixed bed reactor for syngas production.

Steam gasification of two different refuse derived fuels (RDFs), differing slightly in composition as well as thermal stability, was carried out in a fixed-bed reactor at atmospheric pressure. The proximate and ultimate analyses reveal that carbon and hydrogen are the major components in RDFs. The thermal analysis indicates the presence of cellulose and plastic based materials in RDFs. H2 and CO are found to be the major products, along with CO2 and hydrocarbons resulting from gasification of RDFs. The effect of gasification temperature on H2 and CO selectivities was studied, and the optimum temperature for better H2 and CO selectivity was determined to be 725 degrees C. The calorific value of product gas produced at lower gasification temperature is significantly higher than that of gas produced at higher process temperature. Also, the composition of RDF plays an important role in distribution of products gas. The RDF with more C and H content is found to produce more amounts of CO and H2 under similar experimental conditions. The steam/waste ratio showed a notable effect on the selectivity of syngas as well as calorific value of the resulting product gas. The flow rate of carrier gas did not show any significant effect on products yield or their distribution.

Investigation of some large building energy conservation opportunities using the doe-2 model

Owing to their complexity, the design and efficient operation of HVAC systems in commercial buildings can be greatly enhanced by using accurate thermal simulation models. The DOE-2 model was validated using monitored data for a large (28,000 m2) commercial building. The model provided a means to evaluate some conservation measures which included window glazings, occupancy sensors, cold deck temperature set point and reduced ventilation air. Reductions in cold deck temperature and ventilation air were attractive as no-cost options which could be easily returned to original settings if problems arose. The potential energy savings for occupancy sensors was substantial and could prove economical.

Analysis of a Pressure-Compensated Flow Control Valve

A pressure-compensated valve (PC valve) is a type of flow control device that is a combination of a control orifice and a compensator (often called a hydrostat). The compensator orifice modulates its opening to maintain a constant pressure drop across the control orifice. In other words, the PC valve is so designed that the flow rate through the valve is governed only by the opening of the control orifice and is independent of the total pressure drop across the valve. Because of the high nonlinearities associated with this type of valve, it is impossible, in practice, to design such a valve where the flow rate is completely unaffected by the pressure drop across the valve. In this paper, the effect of the nonlinearities on the performance of the PC valve is investigated. First, a generic nonlinear model of a PC valve is developed. Using this model, all possible operating conditions can be determined. Then a linearized model is developed and used to analyze the dynamic behavior of the PC valve. The model can then be used to evaluate and improve the design and operation of the valve for specific applications.

Aerodynamic Separation and Fractional Drying of Alfalfa Leaves and Stems—A Review and New Concept

Abstract This article examines the state-of-the art on aerodynamic separation and drying of leaves and stems. Relevant aerodynamic and drying characteristics of alfalfa leaves and stems, important in the design and functional performance evaluation of appropriate drying and separation systems, are presented. General features and design parameters of rotary drum dryers are discussed. A new efficient approach to combined drying and separation in a rotary drum dryer is described in which fresh or pre-wilted alfalfa mixture is dried at a moderate temperature, and in the same operation the dry leaf fraction is aerodynamically separated from the stem fraction. Preliminary test data obtained from the dryer indicated that the separated product stream had comparatively high leaf purity, confirming the feasibility of the new approach.

An Empirical Discharge Coefficient Model for Orifice Flow

Abstract In fluid power systems, flow control is mainly achieved by throttling the flow across valve orifices. Lumped parameter models are generally used to model the flow in these systems. The basic orifice flow equation, derived from Bernoullis equation of flow, is proportional to the orifice sectional area and the square root of the pressure drop and is used to model the orifice coefficient of proportionality. The discharge coefficient, Cd, is often modeled as being constant in value, independent of Reynolds number. However, for very small orifice openings, Cd varies significantly and can result in substantial error if assumed constant. In this situation, modelers usually revert to graphs or look—up tables to determine Cd. This paper provides a closed form model for Cd as a function of the Reynolds number which can be applied to different types of orifices. Based on this model, a technique to evaluate flow given an orifice area and pressure drop without having to use iteration is introduced.

Method for calculating degree-days to any base temperature

Abstract A simple method is presented for accurately computing the degree-days to any base temperature. The method is based on an assumed annual normal distribution of the daily mean temperatures around the monthly mean temperature. A maximum of prediction error of only 0.28 degree-days per day was observed when compared to actual weather data at four representative locations.

PELLETING CHARACTERISTICS OF FRACTIONATED SUN-CURED AND DEHYDRATED ALFALFA GRINDS

A pilot scale pellet mill was used to produce pellets using ground alfalfa leaf and stem fractions. Both sun-cured and dehydrated alfalfa chops were used in the experiments. The moisture content of the sun-cured and dehydrated chops was 8.4% and 9.6% (w.b.), respectively. A stack of two square sieves with different opening sizes and a pan were used to separate leaf and stem fractions. The leaf and stem fractions were further segregated into two sample lots and ground in a hammer mill using screen sizes of 3.20 and 1.98 mm (1/8 and 5/64 in.). The leaf and stem fractions from each sample lot of same grind sizes were combined to get five different samples with leaf contents ranging from 0% to 100% in 25% increments. The moisture contents and temperatures of the samples were raised to 10% to11% (w.b.) and 76.C, respectively, in a double chamber steam conditioner prior to the pelleting operation. The temperature of material was further raised to 95.C in the pellet mill due to the friction between its roller-die assembly. Average particle sizes of sample lots were determined. Temperatures and moisture contents of samples, after various pelleting stages, were recorded. High durability pellets were produced using fractionated sun-cured alfalfa, irrespective of grind size (except for 100% stems, which was low). Durability fluctuated between high and medium range for dehydrated alfalfa (except for 100% stems, which was low). Greener pellets were produced from dehydrated alfalfa, while harder pellets were produced from sun-cured alfalfa.

PERFORMANCE STUDY OF A RE-CIRCULATING CABINET DRYER USING A HOUSEHOLD DEHUMIDIFIER

ABSTRACT The performance and operating characteristics of a low temperature re-circulating cabinet dryer using a dehumidifier loop were studied using alfalfa. Chopped alfalfa, initially at 70% moisture content, was dried to 10% moisture content in the dryer. Two dryer setups were used. The dryers in each case had a partitioned cabinet with trays of material on one side and a stack of one or two small household dehumidifiers on the other side. Air was re-circulated through the material from bottom to the top and back through the dehumidifiers. Two drying configurations were tested. In one, the material was left on the trays until drying was complete (batch or fixed tray drying). In the other configuration, the trays were moved from top to bottom, introducing a new tray at the top while removing an old tray from bottom. Drying air temperature ranged from 25 to 45°C. The average air velocity through the material was 0.38 m/s. Alfalfa chops dried in 5 h in the fixed tray drying and in 4 h in the moving tray drying. The specific moisture extraction rate ranged from 0.35 to 1.02 kg/kWh for batch drying and stayed at an average value of 0.50 kg/kWh for continuous/moving tray drying.

Modelling of Orifice Flow Rate at Very Small Openings

Abstract Modelling hydraulic control systems that contain flow modulation valves is highly influenced by the accuracy of the equation describing flow through an orifice. Classically, the basic orifice flow equation is expressed as the product of cross-sectional area, the square root of the pressure drop across the orifice and a “flow discharge coefficient”, which is often assumed constant. However, at small Reynolds numbers (such the case of valve pilot stage orifices), the discharge coefficient of the flow equation is not constant. Further, the relationship between the flow cross-sectional area and the orifice opening are extremely complex due to clearances, chamfers, and other factors as a result of machining limitations. In this work, a novel modification to the flow cross-sectional area is introduced and the resulting closed form of the flow equation is presented. As a secondary benefit, an analytical form of the orifice flow gain and flow pressure coefficient can be obtained. This closed form equation greatly facilitates the transient and steady state analysis of low flow regions at small or null point operating regions of spool valve.

The Saskatchewan conservation house: Some preliminary performance results

Abstract The Saskatchewan Conservation House, a low-energy-consumption solar-heated residential structure, began operation in December 1977. Monitoring of the house began in January 1978. The house has been operated as a demonstration dwelling seven days a week, and consequently monitoring conditions have been less than ideal, with approximately 1,000 visitors per week passing through the house. Monitoring of the energy consumption of the dwelling indicates that the design objective — a heat loss rate of 81 Watts per degree Celsius temperature difference between outside and inside — has been met and improved upon. An average Regina house has a heat loss rate of approximately 250 Watts/°C. The system uses 17.8 m2 of vacuum tube collectors. As the system was not started until mid-December, 1977, it was not possible to provide 100% solar heating during this winter period. Approximately three Gigajoules of thermal energy can be stored in the 12,700-litre storage tank. Based on the measured performance of the house, a ‘space-heating requirement of 5.1 Gigajoules per year (4.8 million Btu) would be needed to heat the house under normal occupancy conditions. The system is designed to provide 100% of this space-heating requirement.