A thermodynamic simulation of the power generation gas turbine of the Mosul gas turbine power sta... more A thermodynamic simulation of the power generation gas turbine of the Mosul gas turbine power station was carried out, and its performance was observed. The simulation included detailed modeling of the compressor, the combustion chamber and the turbine based on the physics as well as the common practice in the field. Comparison of the simulation code results with the field collected data indicated agreement to within 2% of the compared parameters. The developed code then used to study the effect of varying the ambient temperature on the performance of the system. The results showed a decrease of up to 21% in the power output when the ambient temperature increases from its ISO value of 15˚C to 45 ˚C. Comparison between running the system under constant turbine inlet temperature and constant turbine power output were also conducted.
Allowing a solar system that is governed by Bang-Bang controllers to cycle is shown to have an ef... more Allowing a solar system that is governed by Bang-Bang controllers to cycle is shown to have an effect on the overall energy collection. An analytical method to evaluate the relative increase in collected energy (RICE) is developed and a design procedure for the selection of the set point ΔTON of the controller is presented. The performance of several case studies is analyzed and the preference of using the duration of cycles rather than the number of cycles, N, in judging the effect of cycling is discussed.
While HVAC maintenance is primarily a technical service, it is provided by people who work for ot... more While HVAC maintenance is primarily a technical service, it is provided by people who work for other people, and is performed for people who own or occupy a building. A maintenance measure is only effective if technicians have the tools, skills and training to implement it properly. Heating, ventilating and air conditioning (HVAC) systems consume the largest portion of energy used in a building. Many building faults that occur during a project life cycle hugely contribute to energy loss, including: operational faults from improper installation, poor testing and commissioning, poor integration with building management systems, equipment degradation, sensor offset failures and control logic problems. They can be grouped into several categories, including: (1) control fault, (2) sensor offset, (3) equipment performance degradation, (4) fouling fault, (5) stuck fault, and others. The present study identified seven factors affected HVAC Maintenance performance that increased the energy c...
The freezing of water around immersed unfinned and finned horizontal tubes is simulated numerical... more The freezing of water around immersed unfinned and finned horizontal tubes is simulated numerically. The impact of natural convection as well as the water density inversion with temperature is considered. The equations governing both fluid flow and heat transfer around the tubes and through the solid–liquid interface are solved using finite difference schemes. To follow the moving solid–liquid boundary, dynamic grid generation is performed using the elliptic partial differential equation method with iterative interpolating smoothing to avoid divergence. For validation, the present results for unfinned tubes are compared with experimental studies reported in the literature. The present numerical simulations are aimed at improving our understanding of the parameters affecting the freezing process around both finned and unfinned tubes. The results showed that the flow patterns are similar in both tube configurations with one main vortex in the liquid region when there is no inversion i...
Convective heat transport coefficients are computed from data obtained from a full-scale test in ... more Convective heat transport coefficients are computed from data obtained from a full-scale test in a closely controlled, passive solar sunspace. The subtractive convective heat transport at the surface is calculated from the conductive and radiative fluxes. Methods for calculating these fluxes from measured data, and estimating best fit coefficients are presented. The results obtained are found to be in very good agreement with an independent approach used to analyze the same data sets.
In the present work, the natural convection heat transfer from horizontal cylinder with square cr... more In the present work, the natural convection heat transfer from horizontal cylinder with square cross section situated in a square enclosure, vented symmetrically from the top and the bottom is investigated experimentally. The experimental work includes temperature measurements of the cylinder surface and the environment during transient state to determine Nu for the unbound and the bound cylinder. The studied variable ranges were: 10 ≤ Ra ≤ 6.6× 10, 2 ≤ W/D ≤ 4, 0.25 ≤ O/D ≤ 4. The results indicated an increase in Nu with increasing Ra. Furthermore, Nu increased proportionally with the vent opening size at low enclosure widths. It showed inverse proportionality with opening size for high enclosure widths. The maximum percentage of the enhancement is more than 20% for bounded square cylinder as compared with unbounded square cylinder. Keywords: Heat Transfer, Square Cylinder, Enclosure, Experimental -./01ا ;<=>?@ A<B CD><E>F G<HIF G<JKF تاذ C<OKBا CPا>J&...
In a prior study, the novel shroud−chimney configuration (SCC) (semicircular shrouds and expended... more In a prior study, the novel shroud−chimney configuration (SCC) (semicircular shrouds and expended chimney) has been numerically demonstrated to passively augment natural convection heat transfer from a horizontal cylinder. However, to implement such a configuration for practical utilizations, the heat flow properties must be experimentally observed and understood. In this work, a controlled experiment is carried out to validate the impact of SCC on heat transfer from a horizontal cylinder subjected to a constant measured heat flux at its inner surface. Circumferential temperature measurements at the cylinder surface, shrouds, and ambient are achieved using thermocouples. The emissivity of the cylinder is measured and utilized to estimate radiation heat loss from the cylinder surface. All presented cases are numerically simulated for validation. The measured and numerically predicted cylinder surface temperatures are within 2% agreement. Moreover, the experimentally and numerically e...
In this work, Natural convection heat transfer from a horizontal cylinder placed in a vented encl... more In this work, Natural convection heat transfer from a horizontal cylinder placed in a vented enclosure was investigated numerically to infer the effect of Rayleigh number (Ra) having the values 1*10 4 , 5*10 4 and 1*10 5 , the effect of the ratio of the enclosure width to the cylinder diameter (W/D) having the values 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3 and 3.5, the effect of the ratio of the vent size to the enclosure width (O/W) for a range starting from 0 for a closed enclosure to 1 for an enclosure having two vertical walls only, and the effect of time variation, on the Nusselt number (Nu), the mass flow-rate, the flow and temperature patterns as well as the boundary layers, where the results showed that, Nu. number always increased with Ra. Number. Furthermore, Nu. number increased with the increase of the ratio W/D for ratios of O/W greater than 0.25, and Nu. number decreases with the increase of W/D for the range below this value.
This research aims at investigating the economics of domestic solar hot water systems in order to... more This research aims at investigating the economics of domestic solar hot water systems in order to promote the use of such systems in Iraq in spite of the low prices of the natural energy sources. The integrated collector storage system, suggested by Kahwaji, is adopted in this study due to its simplicity and good thermal performance especially with respect to nighttime heat loss. Thermal and economics analysis indicated that the system can provide savings of 49 %, 56 %, 35 % and 58 % in the domestic hot water energy expenditure in the environment of the cities of Mosul, Baghdad, Basrah and Ratba respectively when 20 % inflation rate for the price of electricity and a system life time of 20 years are used.
A novel method to passively improve natural convection from a horizontal isothermal cylinder is p... more A novel method to passively improve natural convection from a horizontal isothermal cylinder is proposed and numerically analyzed. The improvement is achieved by using a cylinder configured with se...
A thermodynamic simulation of the power generation gas turbine of the Mosul gas turbine power sta... more A thermodynamic simulation of the power generation gas turbine of the Mosul gas turbine power station was carried out, and its performance was observed. The simulation included detailed modeling of the compressor, the combustion chamber and the turbine based on the physics as well as the common practice in the field. Comparison of the simulation code results with the field collected data indicated agreement to within 2% of the compared parameters. The developed code then used to study the effect of varying the ambient temperature on the performance of the system. The results showed a decrease of up to 21% in the power output when the ambient temperature increases from its ISO value of 15˚C to 45 ˚C. Comparison between running the system under constant turbine inlet temperature and constant turbine power output were also conducted.
Allowing a solar system that is governed by Bang-Bang controllers to cycle is shown to have an ef... more Allowing a solar system that is governed by Bang-Bang controllers to cycle is shown to have an effect on the overall energy collection. An analytical method to evaluate the relative increase in collected energy (RICE) is developed and a design procedure for the selection of the set point ΔTON of the controller is presented. The performance of several case studies is analyzed and the preference of using the duration of cycles rather than the number of cycles, N, in judging the effect of cycling is discussed.
While HVAC maintenance is primarily a technical service, it is provided by people who work for ot... more While HVAC maintenance is primarily a technical service, it is provided by people who work for other people, and is performed for people who own or occupy a building. A maintenance measure is only effective if technicians have the tools, skills and training to implement it properly. Heating, ventilating and air conditioning (HVAC) systems consume the largest portion of energy used in a building. Many building faults that occur during a project life cycle hugely contribute to energy loss, including: operational faults from improper installation, poor testing and commissioning, poor integration with building management systems, equipment degradation, sensor offset failures and control logic problems. They can be grouped into several categories, including: (1) control fault, (2) sensor offset, (3) equipment performance degradation, (4) fouling fault, (5) stuck fault, and others. The present study identified seven factors affected HVAC Maintenance performance that increased the energy c...
The freezing of water around immersed unfinned and finned horizontal tubes is simulated numerical... more The freezing of water around immersed unfinned and finned horizontal tubes is simulated numerically. The impact of natural convection as well as the water density inversion with temperature is considered. The equations governing both fluid flow and heat transfer around the tubes and through the solid–liquid interface are solved using finite difference schemes. To follow the moving solid–liquid boundary, dynamic grid generation is performed using the elliptic partial differential equation method with iterative interpolating smoothing to avoid divergence. For validation, the present results for unfinned tubes are compared with experimental studies reported in the literature. The present numerical simulations are aimed at improving our understanding of the parameters affecting the freezing process around both finned and unfinned tubes. The results showed that the flow patterns are similar in both tube configurations with one main vortex in the liquid region when there is no inversion i...
Convective heat transport coefficients are computed from data obtained from a full-scale test in ... more Convective heat transport coefficients are computed from data obtained from a full-scale test in a closely controlled, passive solar sunspace. The subtractive convective heat transport at the surface is calculated from the conductive and radiative fluxes. Methods for calculating these fluxes from measured data, and estimating best fit coefficients are presented. The results obtained are found to be in very good agreement with an independent approach used to analyze the same data sets.
In the present work, the natural convection heat transfer from horizontal cylinder with square cr... more In the present work, the natural convection heat transfer from horizontal cylinder with square cross section situated in a square enclosure, vented symmetrically from the top and the bottom is investigated experimentally. The experimental work includes temperature measurements of the cylinder surface and the environment during transient state to determine Nu for the unbound and the bound cylinder. The studied variable ranges were: 10 ≤ Ra ≤ 6.6× 10, 2 ≤ W/D ≤ 4, 0.25 ≤ O/D ≤ 4. The results indicated an increase in Nu with increasing Ra. Furthermore, Nu increased proportionally with the vent opening size at low enclosure widths. It showed inverse proportionality with opening size for high enclosure widths. The maximum percentage of the enhancement is more than 20% for bounded square cylinder as compared with unbounded square cylinder. Keywords: Heat Transfer, Square Cylinder, Enclosure, Experimental -./01ا ;<=>?@ A<B CD><E>F G<HIF G<JKF تاذ C<OKBا CPا>J&...
In a prior study, the novel shroud−chimney configuration (SCC) (semicircular shrouds and expended... more In a prior study, the novel shroud−chimney configuration (SCC) (semicircular shrouds and expended chimney) has been numerically demonstrated to passively augment natural convection heat transfer from a horizontal cylinder. However, to implement such a configuration for practical utilizations, the heat flow properties must be experimentally observed and understood. In this work, a controlled experiment is carried out to validate the impact of SCC on heat transfer from a horizontal cylinder subjected to a constant measured heat flux at its inner surface. Circumferential temperature measurements at the cylinder surface, shrouds, and ambient are achieved using thermocouples. The emissivity of the cylinder is measured and utilized to estimate radiation heat loss from the cylinder surface. All presented cases are numerically simulated for validation. The measured and numerically predicted cylinder surface temperatures are within 2% agreement. Moreover, the experimentally and numerically e...
In this work, Natural convection heat transfer from a horizontal cylinder placed in a vented encl... more In this work, Natural convection heat transfer from a horizontal cylinder placed in a vented enclosure was investigated numerically to infer the effect of Rayleigh number (Ra) having the values 1*10 4 , 5*10 4 and 1*10 5 , the effect of the ratio of the enclosure width to the cylinder diameter (W/D) having the values 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3 and 3.5, the effect of the ratio of the vent size to the enclosure width (O/W) for a range starting from 0 for a closed enclosure to 1 for an enclosure having two vertical walls only, and the effect of time variation, on the Nusselt number (Nu), the mass flow-rate, the flow and temperature patterns as well as the boundary layers, where the results showed that, Nu. number always increased with Ra. Number. Furthermore, Nu. number increased with the increase of the ratio W/D for ratios of O/W greater than 0.25, and Nu. number decreases with the increase of W/D for the range below this value.
This research aims at investigating the economics of domestic solar hot water systems in order to... more This research aims at investigating the economics of domestic solar hot water systems in order to promote the use of such systems in Iraq in spite of the low prices of the natural energy sources. The integrated collector storage system, suggested by Kahwaji, is adopted in this study due to its simplicity and good thermal performance especially with respect to nighttime heat loss. Thermal and economics analysis indicated that the system can provide savings of 49 %, 56 %, 35 % and 58 % in the domestic hot water energy expenditure in the environment of the cities of Mosul, Baghdad, Basrah and Ratba respectively when 20 % inflation rate for the price of electricity and a system life time of 20 years are used.
A novel method to passively improve natural convection from a horizontal isothermal cylinder is p... more A novel method to passively improve natural convection from a horizontal isothermal cylinder is proposed and numerically analyzed. The improvement is achieved by using a cylinder configured with se...
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