Impact of Implementing a Dedicated Outdoor Air System in Parallel with a Multi-Zone Variable-Air Volume System on Energy Consumption, Thermal Comfort, and Life Cycle Cost

Heating, Ventilating, and Air-Conditioning systems (HVAC) consume more than 40% of energy in commercial buildings, according to the Commercial Building Energy Consumption Survey in 2012. Therefore, efforts to reduce HVAC energy consumption would be significant in coping with energy-related issues. In that context and in order to enhance the indoor air quality without compromising for energy consumption, the concept of Dedicated Outdoor Air systems (DOAS) emerged. The literature shows that the integration of DOAS with other HVAC systems has been studied widely, yet the impact of integrating DOAS in parallel with multi-zone Variable-Air Volume systems (multi-zone VAV) for an application requiring high ventilation air has not been researched. Therefore, the objective of this study was to assess the impact of the integration from various aspects. For assessing the impact of implementing DOAS in parallel with multi-zone VAV, a primary school model was simulated in 17 climate zones and in 6 HVAC configurations. The simulations were conducted for conditions of 8,760 hours/year, and their results were compared to the results of a baseline model utilizing multi-zone VAV for handling the ventilation load besides handling the thermal local loads. The assessment considered the impact on energy consumption, thermal comfort, and life cycle cost. The results showed a saving in HVAC energy in all considered climate zones when the DOAS supplied ventilation air at 12.8-15.6o C Dry Bulb Temperature (DBT) and 12.8o C Dew Point Temperature (DPT). The saving in energy ranged from 4% to 40%. In addition, the climate zones with low outdoor latent loads experienced high changes in energy consumption compared to the climate zones with high outdoor latent loads. In terms of the change in thermal comfort, the Fanger Comfort Model was utilized to observe the change from the occupant perspectives. The change among the various configurations did not show a significant difference; the maximum percentage of occupants who would have experienced a difference in the thermal comfort was less than 0.5% in all climate zones. Economically, the energy cost would decrease in a configuration supplying ventilation air through DOAS with conditions of 12.8-15.6o C DBT and 12.8o C DPT in all considered climate zones. In this study, the saving in energy cost ranged from $500/year to$ 6,000/year. Moreover, multi-zone VAV units could be downsized significantly. However, the saving would not have been encouraging economically when it was considered for overcoming the cost of implementing DOAS; the payback period was 11 years at the best, only for owning DOAS units without other costs associated with the DOAS implementation

Dynamic Modeling of Packaged Air Conditioner with Micro-Channel Heat Exchanger Condenser

Microchannel Heat Exchangers (MCHX) are used in Air Conditioning systems (AC) as an efficient type of Heat Exchangers (HX) because they have compact size, as well as low refrigerant charge. However, using MCHX as condensers can be associated with some problems, including evaporatorcondenser transient charge balance issues. Therefore, this study aims to investigate the impact of using MCHX as a condenser in a packaged air conditioner with a finandtube heat exchanger as an evaporator. The methodology was dynamically modeling the packaged air conditioner in Modelica, considering varying pass configurations of MCHX with several refrigerant charges. The results showed that the pressure in the highpressure side of the refrigerant cycle increases as the number of tubes in the inletpass of the MCHX decreases. In addition, if the difference in the number of tubes among the inletpass and the outletpass is large, the pressure increases regardless of which pass has the highest number of tubes. Moreover, the pressure can increase after a while at the beginning of an oncycle due to the slow response of Thermostatic Expansion Valve (TXV) caused by the thermal inertia of the sensing bulb. We defined a mass ratio as mass of refrigerant in the evaporator to the mass in the condenser. A decrease in the mass ratio for a given total charge corresponds to the refrigerant accumulating in the condenser, increasing pressure in the condenser

Effect of Inlet Duct Design on Fan Performance of Indoor Air Handling Units with Pull-Through Fan Configuration (ASHRAE RP-1743)

During testing indoor air handling units, ASHRAE Standard 37 requires installing an inlet duct that might increase the length of the testing setup to exceed the capability of some testing facilities. ASHRAE Research Project 1743 (ASHRAE RP1743) addresses this issue by evaluating the effect of inlet duct design on fan performance of indoor air handling units. The findings of the study will allow identifying alternative, shorter, inlet duct configurations maintaining the fan performance as of that obtained with ASHRAE Standard 37 inlet duct. The test matrix of the project includes various indoor units differing in motor type, such as Constant Torque Motor (CTM) and Electronically Commutated Motor (ECM), and fan configurations, such as pullthrough and pushthrough configuration. This paper focuses on the findings of testing two pullthroughfanconfiguration units, one of which with a CTM fan and the other with an ECM fan. In addition, other effects, such as atmospheric pressure and hysteresis in approaching external static pressure (ESP), were investigated to study their impacts on the repeatability of equipment testing. The results of the CTMfan unit showed that the proposed alternative inlet duct configurations can maintain the fan performance within the suggested tolerances, which are 5% in power and 2.5% in air volumetric flowrate relative to the ASHRAE Standard 37 inlet duct. This allows a reduction in the inlet duct stacklength from 38% to 74% compared to ASHRAE Standard 37 inlet duct configuration. Noticeable performance hysteresis was observed at low air flowrate and ESP, while atmospheric pressure had no effect on fan performance. For the ECMfan unit, the fan performance was maintained during testing the proposed alternative inlet duct configurations within the suggested tolerance, with a noticeable decrease in power during testing the reduced alternative inlet duct configuration. The reduction in the stack length as compared to the standard inlet duct configuration was 40%, 72%, 74% for the inlet box, 4inch inlet duct, and reduced alternative configuration, respectively. In contrast to the results of the CTMfan unit, the hysteresis effect on the ECMfan unit was found to be insignificant, while atmospheric pressure effect was significant. As the atmospheric pressure increased, air volumetric flowrate and fan’s power decreased

A Software Defined paradigm for mobile networks: A feasible SDN based architecture solution for 5G networks

University of Technology Sydney. Faculty of Engineering and Information Technology.As the mobile networks evolve towards 5G, the infrastructure network will have the capability to handle operational complexities and support unforeseen services that are diverse and likely to grow with demand for applications that include M2M (machine-to-machine) modules, video surveillance, smart cities, mobile industrial automation, and vehicle connectivity \cite{Hakiri2015}. These applications include requirements that are divergent and will trigger mobile network performance and capabilities requirements at their extremity with more scalability and flexibility to be included. SDN technology using cloud computing as a carrier will play a critical and enabling role in designing the 5G wireless networks for Quality of Experience (QoE), service performance and network resilience as parameters to give greater freedom for balanced operations in these networks. In this thesis, an investigation was carried out with the Software-Defined Network (SDN) controllers architecture for addressing many of IP Mobility issues primarily focusing on handover optimisation case studies. It is demonstrated through handover network simulations that SDN can handle next-generation mobility handover situations with the help of proper SDN interfacing, control layout and control logic algorithms. The experiments conducted predominantly benefitted from the OpenFlow protocol based SDN control and data forwarding plane as a proof of concept for deploying into real-world devices for mobile network management. The simulations showed a definite and considerable performance gain when using SDN based solution compared to the traditional Mobile IP for mobility management from the perspective of the user equipment. To accomplish a realistic simulation goal, careful consideration was given while selecting a network emulation platform which is flexible and can be modified and extended easily by external simulation processing modules. Mininet-WiFi emulator was selected and by synthesising SDN architecture a number of functionalities were implemented for the emulator which allowed designing realistic mobile network mobility use case scenarios and also scenarios pertaining to 5G networks applications for the network simulations. All the simulations carried out were extensively substantiated by the mobile network and SDN literature studies and reviews which helped define simulation parameters appropriately

Mechanical and Microstructure Characteristics of Concrete-Mixtures Designed for Durability of RC-Structures in Corrosive Environment

As exposures to chloride-salts are known as prime factors causing initiation and continuity of corrosion-process of steel reinforcement bars in reinforced concrete (RC) structures, it has always been a major concern for designers considering the requirements of structural-durability for targeted-service life of RC-structures in aggressively corrosive environments typically prevalent in coastal regions. Research works previously reported by the researchers have modeled corrosion-process in terms of corrosion-current density, and it was realized that concrete-mixtures design quality and characteristics, degree of exposures to corrosive-agents such as chloride salts, and protective-concrete cover-thickness are now known beyond doubt to be determinant factors as regards RC-structures durability. This research paper is focused on presenting highlights of an extensive experimental investigation carried out on a large number of concrete specimens that were designed, and placed in chloride-salt solution simulating exposure to corrosion-conditions. Results presented in this paper include close-looks at mechanical and micro-structure characteristics with regard to the influence of key design-parameters and exposure-conditions used for test-specimens with various combinations of cementitious materials constituents and proportioning using three replicate-combinations of water-cementitious ratios, fine to total aggregate ratio, and concrete-cover thickness, and with different concentrations of chloride-solution. Statistical analysis of results obtained from a three-year test-program is outlined in terms of one unifying corrosion-process progress indicator, namely, corrosion-current density Icorr, determined by both electrochemicalmethod and gravimetric weight-loss method. The paper presents a general overview of the test program and a summary of sample results on mechanical, strength, and microstructural characteristics obtained from test specimens

Understanding Saudi’s preferences of emergency physicians attire a cross-sectional study

Background: Patient centered care (PCC) is defined as the practice of attending to patients that includes listening, informing, and involving patients in their health care as per picker’s eight principles. A part of the patients’ rights is the presentation of the caring physician which includes attitude and attire. In Saudi Arabia, it has been known that doctors present with white coat. Several studies showed that physician dress-code improve patients’ satisfaction. Our aim in this study is to identify Saudi population preference on the attire of emergency physicians. Methods: This was cross-sectional study in Riyadh, Saudi Arabia. Questions were asked to Saudi population in malls and hospital’s waiting areas regarding physician attire by online survey. Participants were asked demographic questions then they were asked in detail about their preferences. Results: Total 486 participated in the study, where 52.15% strongly care about emergency physician’s look. 82% would like to see their male physician wearing scrubs/medical coat, 43% agreed on a face cover for their female physician but still prefer scrubs/medical coat with 45%.  Lastly participants had equal thoughts when it came to experience and reliability as 38% agree that looks can affect these two qualities. When it came to the relation of looks to knowledge as percentage were very close with 31% neutral and 32% agreed. Conclusions: Both Saudi sexes equally consider emergency physician external look as a representation on their respectfulness, reliability, and experience, but not that significant to the knowledge he has

Mucosa-Associated Lymphoid Tissue Lymphoma of the Lacrimal Gland: Sustained Remission after Eradication of Helicobacter Pylori Infection

Mucosa-associated lymphoid tissue (MALT) lymphoma is the third most common non-Hodgkin lymphoma, and it is strongly associated with helicobacter pylori infection of the stomach. MALT lymphoma of the lacrimal gland usually presents as a localized disease process in extranodal tissues. The treatment options of MALT lymphoma of the lacrimal gland chiefly include radiation of the tumor, chemotherapy, surgical removal, or a combination of these strategies. We report a case of localized MALT lymphoma of the lacrimal gland, with prolonged sustained remission after eradication of gastric Helicobacter pylori (H. Pylori) infection. He sustains in remission of lacrimal MALT lymphoma for four years without chemotherapy or radiotherapy

Prevalence And Risk Factors of Eye Allergies Among Adults In Ksa: A Cross-Sectional Study

Objective: To determine the prevalence of eye allergies and associated risk factors among adults in KSA. Methods: This research employs a cross-sectional study design to assess the prevalence and risk factors of eye allergies among adults in the Kingdom of Saudi Arabia (KSA). A cross-sectional approach allows for the collection of data at a single point in time, providing a snapshot of the condition's status within the study population. Results: The study included 640 participants. The most frequent age among them was 18-28 years (n= 331, 51.7%), followed by 40-50 years (n= 139, 21.7%). The most frequent gender among study participants was female (n= 389, 60.8%) followed by male (n= 251, 39.2 The most frequent nationality among study participants was Saudi (n= 613, 95.8%) followed by non-Saudi (n= 27, 4.2%). The educational level among study participants with most of them being the university (n= 553, 86.4%) followed by the school (n= 85, 13.3%). The work nature among study participants with most of was inside the building. Participants were asked if they had an eye problem that affected their daily life. The most frequent answer was moderately (n= 309, 48.3%) followed by never (n= 271, 42.3%), and the least was a lot (n=60, 9.4%).  Conclusion: The results of the study showed that most of the study participants are Saudis and most of them work inside the building. The majority have university education, and the largest percentage of participants are women. Most of the participants are non-smokers. Most study participants had good social communication

Partial Nephrectomy A Comparison between Different Modalities

Kidney cancer, with 4% of all malignancies, is one of the most common malignancies occurring among in adults. In Saudi Arabia, kidney cancer comprises 2.3% of all cancers, and its incidence has increased by 33%. Partial nephrectomy (PN) is considered as the gold standard for T1 renal masses. In this retrospective study, we did a chart review for all patients who underwent PNs between April 2013 and February 2019. Data comprised pre-sentation, tumor size, type of procedure (open vs. laparoscopic vs. robotic), and intra- and post-operative complications. Chi-square, ANOVA, and cross-tabulation were done using SPSS software. P > 0.05 was considered significant. Approval was obtained from the institutional review board of King Abdullah International Medical Research Center. In all, 69 patients were identified: 26 (37.7%) males and 43 (62.3%) females, with mean age = 54.53 ± 13.21 years; mean body mass index = 32.36 ± 7.03, and mean tumor size = 3.7 ± 1.72 cm. In terms of presentation, most patients (50, 72.4%) presented incidentally as opposed to symptomatic presentation. Of these patients, 18 (26.1%) underwent open partial nephrectomy (OPN), 29 (42%) laparoscopic partial nephrec-tomy (LPN), and 22 (31.9%) robotic partial nephrectomy (RPN). On comparing minimally invasive surgery (MIS) PN with OPN, we found that OPN had more blood loss and a longer hospital stay but a shorter operating room (OR) time. Results of PN irrespective of the procedure type, whether it was OPN, LPN, or RPN, were similar if performed by experienced surgeons. However, open procedures involved a higher blood loss, more operative time, and longer hospital stay when compared with minimally invasive techniques