An Evaluation of Heat Exchangers Using System Information and PEC

This report describes analyses aimed at integrating component optimization and system design by developing heat-exchanger performance evaluation criteria (PEC) that account for the system-level performance impacts of heat exchanger design. It builds on earlier studies that used relatively simple PEC to capture some of the component-level tradeoffs, but which usually ignore the system impact of component design. This report evaluates four PEC-j/f, heat transfer/pumping power (8), heat transfer/(pumping + compressor power) (n), and system COP. It is shown that j/f and 8 are better used as comparison criteria for existing heat exchangers of equal heat duty rather than as design criteria. The other two PEC, n and COP, include the system effect of compressor efficiency and therefore can be used more effectively in heat exchanger and system design. Through a combination of PEC and system optimization techniques, a method is developed to evaluate and design heat exchangers for maximum system performance.Air Conditioning and Refrigeration Project 9

Benchmark footbridge for vibration serviceability assessment under vertical component of pedestrian load

Vibration serviceability criteria are governing the design and determining the cost of modern, slender footbridges. Efficient and reliable evaluation of dynamic performance of these structures usually requires a detailed insight into the structural behaviour under human induced dynamic loading. Design procedures are becoming ever more sophisticated and versatile and for their successful use a thorough verification on a range of structures is required. The verification is currently hampered by a lack of experimental data that are presented in the form directly usable in the verification process

Evaluating the Performance of Bioclimatic Design Building in Nigeria

Bioclimatic design is an important strategy toward achieving sustainable building. Through the implementation of bioclimatic concept in buildings, energy demand can be reduced leading to increased users satisfaction. Using a set of questionnaire, a bioclimatic design evaluation was conducted to assess the satisfaction and perception of occupants in a residential building with the best practice of bioclimatic design strategies, particularly natural ventilation and daylighting. The questionnaire was based on a five-point Likert scale, covering various performance criteria of building, specifically on the architectural elements of thermal comfort, indoor air quality, visual comfort, acoustic comfort and landscape elements. Findings showed a positive relationship between perceptions and building performance criteria. Keywords: Bioclimatic design; Performance evaluation; Satisfaction and perception; Nigeri

Helicopter noise: Blade slap. Part 2: Experimental results

Blade slap encountered in rotary wings and its effect on helicopter performance are reported. The results of various individual flight tests are presented and, where possible, correlated with one another. Observations from the subjective evaluation of blade slap are included, together with a modified form of the blade slap factor (BSF) which can be used as a design criteria

Performance criteria guideline for three explosion protection methods of electrical equipment rated up to 15,000 volts AC

The Bureau of Mines, U.S. Department of the Interior, is reviewing explosion protection methods for use in gassy coal mines. This performance criteria guideline is an evaluation of three explosion protection methods of machines electrically powered with voltages up to 15,000 volts ac. A sufficient amount of basic research has been accomplished to verify that the explosion proof and pressurized enclosure methods can provide adequate explosion protection with the present state of the art up to 15,000 volts ac. This routine application of the potted enclosure as a stand alone protection method requires further investigation or development in order to clarify performance criteria and verification certification requirements. An extensive literature search, a series of high voltage tests, and a design evaluation of the three explosion protection methods indicate that the explosion proof, pressurized, and potted enclosures can all be used to enclose up to 15,000 volts ac

Product design concept evaluation by using analytical hierarchy and analytical network processes

The aim of this study is to improve the success and efficiency of the design concept evaluation and selection activity in industrial design by adapting two specialized evaluation-selection methods to the design process and comparatively demonstrating their use. The methods are called the Analytic Hierarchy Process (AHP) and the Analytic Network Process (ANP). In their application, first the main design objective is decided upon and the evaluation criteria are determined accordingly, followed by the listing of the design concept alternatives. Then the criteria's importance values as well as relations between them are investigated and evaluation of the alternatives is done according to the criteria by using the tools provided by the methods. The application presented in the article evaluates seven hand cart designs by using the two methods. First the tasks that are common in both methods, then the tasks specific to each method are explained. The general criteria to be used in the evaluation are identified and the effects of these criteria on the evaluation process are determined through interviews with designers and users participating in the study. Then the relative performance rankings of the available seven hand cart alternatives are calculated by using both methods. Numerical results are listed in a descending order to show the success levels of the design concepts, pointing to the one that received the highest overall performance. The findings obtained from two methods are comparatively interpreted

Towards energy-autonomous wake-up receiver using visible light communication

The use of Visible Light Communication (VLC) in wake-up communication systems is a potential energy-efficient and low-cost solution for wireless communication of consumer electronics. In this paper, we go one step further and propose the use of visible light both for wake-up communication and energy harvesting purposes, with the final objective of an energy-autonomous wake-up receiver module. We first present the details and the design criteria of this novel system. We then present the results of evaluation of design criteria such as solar panel and capacitor type choices. To evaluate the performance of the developed wake-up system with energy-autonomous receiver system, we perform realistic indoor scenario tests, analyzing the effect of varying distances, angles, and light intensities as well as the effect of presence of interfering lights.Peer ReviewedPostprint (author's final draft

Contracting Strategies: A Different Approach to Address Long-term Performance

For cost-efficiency, public safety, and sustainability, improving long-term performance in highway projects is imperative for public administrations. Project delivery and procurement methods provide an opportunity to align design and construction processes with this goal. While previous studies have explored whether project delivery methods impact the long-term performance of highway projects, these studies did not focus on how core elements within project procurement relate to long-term performance. Thus, to fill this gap, this research explores how and to what extent long-term evaluation criteria are considered in design-build best-value procurement of highway projects. To this end, the team conducted content analysis on 100 projects procured between 2009 and 2019 by 19 DOTs across the U.S. The analysis of 365 evaluation criteria found that (1) roughly 11% of them related to long-term performance. (2) The weight given to these criteria in the overall technical proposal was lower than 30%. (3) Sixty-five percent (65%) of long-term evaluation criteria focused on design while 15% related to materials and technology, respectively. The results of this study are a stepping stone to initiate a deep exploration of the relationship between procurement practices and actual project performance. Currently, as sustainability and life cycle assessments remain top concerns in infrastructure projects, this line of research may benefit DOTs and highway agencies across the U.S. and worldwide

Solar dynamic heat rejection technology. Task 1: System concept development

The results are presented of a concept development study of heat rejection systems for Space Station solar dynamic power systems. The heat rejection concepts are based on recent developments in high thermal transport capacity heat pipe radiators. The thermal performance and weights of each of the heat rejection subsystems is addressed in detail, and critical technologies which require development tests and evaluation for successful demonstration are assessed and identified. Baseline and several alternate heat rejection system configurations and optimum designs are developed for both Brayton and Rankine cycles. The thermal performance, mass properties, assembly requirements, reliability, maintenance requirements and life cycle cost are determined for each configuration. A specific design was then selected for each configuration which represents an optimum design for that configuration. The final recommendations of heat rejection system configuration for either the Brayton or Rankine cycles depend on the priorities established for the evaluation criteria

Safety assessment for EPS electron-proton spectrometer

A safety analysis was conducted to identify the efforts required to assure relatively hazard free operation of the EPS and to meet the safety requirements of the program. Safety engineering criteria, principles, and techniques in applicable disciplines are stressed in the performance of the system and subsystem studies; in test planning; in the design, development, test, evaluation, and checkout of the equipment; and the operating procedures for the EPS program