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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

White food-type sorghum in direct-expansion extrusion applications

Acosta Sanchez, David 30 September 2004 (has links)
Whole sorghum kernels were directly processed into whole grain snacks with acceptable texture. Extrudates made from whole sorghum had a harder gritty texture than those made from decorticated materials. Extrusion of whole sorghum provides significant savings in processing: there are no dry matter losses; no equipment or energy is required for decortication or milling; the extruder consumes less power and processes more material per time unit. In addition, the extruder utilized is a simple adiabiatic, friction extruder of relatively low cost. Grinding whole sorghum and removing fines did not improve product expansion during extrusion but altered the gritty pieces in the extrudates. The best products were obtained when whole sorghum (ground or un-ground) was extruded at 14% moisture. The whole sorghum extrudates had larger bubbles with thick cell walls, which made extrudates more crunchy. Decortication of sorghum improved extrusion performance and products by allowing adequate formation and retention of air cells. Decortication to remove 20% of the original sorghum weight was enough to produce extrudates with characteristics comparable to those made from commercial yellow corn meal. Sorghum milled fractions with composition and particle size distribution similar to corn meal produced extrudates with higher expansion, lower bulk density and similar texture. In addition, sorghum extrudates were rated equal to corn meal extrudates by a taste panel for appearance, flavor, texture and overall characteristics. Extrudates made from polished rice were less expanded and whiter than extrudates made from sorghum. When processed under similar conditions, sorghum extrusion required more energy than corn meal extrusion. However, whole sorghum extrusion required less energy than corn meal extrusion. Unground sorghum samples (decorticated or non-decorticated) produced harder extrudates compared to those made from ground raw material. White sorghum is a feasible option for snack extrusion because of its versatility, product characteristics, cost and processing properties.
2

White food-type sorghum in direct-expansion extrusion applications

Acosta Sanchez, David 30 September 2004 (has links)
Whole sorghum kernels were directly processed into whole grain snacks with acceptable texture. Extrudates made from whole sorghum had a harder gritty texture than those made from decorticated materials. Extrusion of whole sorghum provides significant savings in processing: there are no dry matter losses; no equipment or energy is required for decortication or milling; the extruder consumes less power and processes more material per time unit. In addition, the extruder utilized is a simple adiabiatic, friction extruder of relatively low cost. Grinding whole sorghum and removing fines did not improve product expansion during extrusion but altered the gritty pieces in the extrudates. The best products were obtained when whole sorghum (ground or un-ground) was extruded at 14% moisture. The whole sorghum extrudates had larger bubbles with thick cell walls, which made extrudates more crunchy. Decortication of sorghum improved extrusion performance and products by allowing adequate formation and retention of air cells. Decortication to remove 20% of the original sorghum weight was enough to produce extrudates with characteristics comparable to those made from commercial yellow corn meal. Sorghum milled fractions with composition and particle size distribution similar to corn meal produced extrudates with higher expansion, lower bulk density and similar texture. In addition, sorghum extrudates were rated equal to corn meal extrudates by a taste panel for appearance, flavor, texture and overall characteristics. Extrudates made from polished rice were less expanded and whiter than extrudates made from sorghum. When processed under similar conditions, sorghum extrusion required more energy than corn meal extrusion. However, whole sorghum extrusion required less energy than corn meal extrusion. Unground sorghum samples (decorticated or non-decorticated) produced harder extrudates compared to those made from ground raw material. White sorghum is a feasible option for snack extrusion because of its versatility, product characteristics, cost and processing properties.
3

Numerical Analysis of a PV/Microchannel Integrated CO2 Direct-Expansion Heat Pump Water Heater

Rony, Mohammad Rajib Uddin January 2019 (has links)
A steady-state numerical model of a PV/microchannel integrated direct-expansion CO2 heat pump (PV-DXHP) water heater is developed, validated, and analyzed in the present study. To accomplish the objectives, a numerical model of a microchannel evaporator integrated into a CO2 PV DXHP is developed and validated. The effects of evaporator operating parameters on the heat absorption and pressure drop are analyzed. Utilizing the evaporator model, the PV-DXHP model is developed, and the baseline values of the heat pump operating parameters are determined from the evaporator parametric study. The PV-DXHP demonstrates high water heating capability, while maintaining a reasonably high COP. The COP has the highest dependency on the CO2 mass flow rate, while the water outlet temperature has the highest dependency on the water mass flow rate. The results are highly promising and indicate the system has potential to help meet the energy requirements for residential and industrial water heating demands.
4

Low energy air conditioning for hot climates

Almutairi, Hamad Hhn January 2012 (has links)
Fossil fuels are the major sources of electrical power generation in the world. Among all fossil fuels, oil is considered as the most sought-after fuel. The burden on countries that provide subsidized electricity produced from oil-fired power plants is noteworthy. Kuwait is a notable example of these countries. Electricity in Kuwait is heavily consumed by residential air conditioning, which comprises 60% of the total electricity generated at peak times on a hot summer day. From this perspective, residential air conditioning in Kuwait was selected to undergo further investigation regarding low energy air conditioning choices. Three solutions to control the rapid growth of demand for electricity by residential air conditioning are examined. The first solution investigated assesses the orientation and grouping of houses in Kuwait in order to examine their effect on cooling load and electrical energy consumption for future houses. Four residential cases were developed; each case comprises six typical houses. The cases identified are: (1) single block facing east-west, (2) single block facing north-south, (3) double block facing east-west and (4) double block facing north-south. Cooling loads are calculated using the DesignBuilder building thermal simulation software. Case (2) is found to have the smallest cooling load, and case (1) the largest. The estimated savings from applying case (2) compared to the average of the four cases for the future houses planned to be built by the government by the year 2016 (i.e. approximately 20,000 houses) are found to be approximately .US 33 million of power system capital costs, 15 GWh per year of electrical energy consumption and 11 kilotons per year of CO2 emissions. In the second solution, a lifecycle cost analysis is performed to evaluate the economic feasibilities of electricity driven chilled water system compared to predominant air conditioning system in Kuwaiti houses which is Packaged- Direct Expansion. The study considers the total cash paid by the consumer and the total cash paid by the government, since electricity is subsidized in Kuwait. The study finds that the chilled water system is not cost-effective for consumers due to high installation cost. However, a chilled water system would be cost-effective for the government because it consumes 40%less electrical energy than Packaged-DX. So, the study suggests subsidising the installation of chilled water systems so that the installation cost to the consumer is the same as for Packaged-DX systems. In the third solution, the study examines the viability of a single-effect LiBr absorption chiller driven by steam extracted from the steam turbine in the configuration of a combined cycle power plant (CCPP). The analysis shows that CCPP with absorption chiller yields less net electrical power available to utility grid compared to similar CCPP giving electricity to the grid and to Direct-Expansion air conditioning systems for the same cooling requirements. The reasons for that are the reduction in steam turbine power output resulted from steam extraction, and the amount of electrical energy required to operate the configuration of CCPP with absorption chiller.

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