Search results for "fault"

Getting insights into the behavior of variable speed direct expansion air conditioning systems under faulty operating conditions

2019

Direct expansion air conditioning systems, such as rooftop units, are widely adopted in small and medium scale commercial buildings. In order to increase the energy performance of these systems during part-load operation, variable-speed compressors and fans have been adopted in the last two decades. However, profitable energy saving could be achieved not only by optimizing the design and the control of these systems, but also by scheduling a proper maintenance strategy. In fact, if not properly maintained, no benefits would be achieved even when more sophisticated systems are adopted. In order to support plant owners in scheduling cost-effective maintenance program, Fault Detection and Diag…

Novel Fault-Tolerant Routing Technique for ZMesh Topology based Network-on-Chip Design

2020

This paper proposes a novel fault-tolerant routing technique for ZMesh topology based Network-on-Chip (NoC) design. The proposed algorithm caters the link faults and routes the data packets seamlessly to the destination. This algorithm has been compared with the existing techniques proposed for mesh topology counterparts. The experimentations have been carried out by increasing ZMesh network size and percentage of link faults. The results show that in the event of link failures the proposed algorithm routes the data from source to destination flawlessly.

Safety analysis in the LBE-Cooled XADS plant through an integrated use of HAZOP, FAULT TREE and thermalhydraulic transient analyses

2004

A detailed description of possible accidental scenarios, with their frequency of occurrence and their consequences, taking into account both internal and external causes that might contribute to them, can be attained by using the most important risk analysis methodologies (HAZard and OPerability studies, HAZOP; Event Tree, ET; Fault Tree, FT; etc.). As it is known, the Fault Tree methodology is aimed at the evaluation of the frequency of an undesired accidental event (Top Event, TE), and is used to describe this one as a combination of primary events identified, for example, by a HAZOP analysis [1]. However, the classic HAZOP analysis, while allowing to perform an exhaustive study of the ex…

A study of mobility and reachability in ad hoc networks using stochastic activity networks

2006

The integration of ad-hoc networks into real environments is now becoming more and more common and supervision and control systems are no exception. The efficiency of the communication in these networks as well as various other factors, are governed by the working area, the number of nodes, mobility, transmission power, etc. In this paper, the mobility and reachability of mobile nodes appearing spontaneously in a large installation such as can be found in a water purification system are studied. These nodes form an ad-hoc network and communicate between each other in order to finally reach a fixed node which can offer them information from the rest of the system in real time or act as a gat…

INNOVATIVE APPLICATIONS OF EXERGY ANALYSIS AND THERMOECONOMICS IN CHEMICAL, THERMAL AND COOLING ENERGY CONVERSION SYSTEMS

Since 70s, the world has been becoming more and more concerned about energy and environmental issues. The need of meeting the current energy demand by guaranteeing the ability of future generation to satisfy theirs have been pushing research not only to exploit alternative energy sources such as renewable energies, but also to improve the efficiency of energy conversion systems. To this regard, developing systems that use efficiently energy is of paramount importance especially in those countries which rely on non-renewable energy sources such as oil, natural gas, and coal. In fact, the reduction of energy consumption will lead not only to the saving of unrestorable and limited energy resou…

Assessing the Robustness of Thermoeconomic Diagnosis of Fouled Evaporators: Sensitivity Analysis of the Exergetic Performance of Direct Expansion Coi…

2016

Thermoeconomic diagnosis of refrigeration systems is a pioneering approach to the diagnosis of malfunctions, which has been recently proven to achieve good performances for the detection of specific faults. Being an exergy-based diagnostic technique, its performance is influenced by the trends of exergy functions in the “design” and “abnormal” conditions. In this paper the sensitivity of performance of thermoeconomic diagnosis in detecting a fouled direct expansion coil and quantifying the additional consumption it induces is investigated; this fault is critical due to the simultaneous air cooling and dehumidification occurring in the coil, that induce variations in both the chemical and th…

SETUP OF VIRTUAL EXPERIMENTS AND CRITICAL ANALYSIS OF CONVENTIONAL THERMOECONOMIC DIAGNOSIS OF MULTIPLE FAULTS IN AIR-CONDENSED ROOFTOP SYSTEMS

2012

The diagnosis of soft faults in vapor compression cooling systems is a crucial activity, since malfunctions may provoke heavy degradation in plant performance and increase the power consumption for space cooling. Among the various Faults Detection and Diagnosis techniques developed over the last two decades, thermoeconomic diagnosis has been playing only a marginal role due to the difficulties encountered when applying the conventional thermoeconomic approaches to vapor compression refrigeration plants. In this paper a critical analysis on capabilities and limits of thermoeconomic diagnosis of refrigeration systems is proposed. The reference plant assumed for this study is a 116 kWc air-con…

Performance maps for an air-cooled air conditioning system as a preliminary instrument for the diagnosis of evaporator fouling

2019

Abstract During the past few decades, there has been increased interest in the development of automated approaches for detecting and diagnosing faults in air conditioning systems. Among them, thermoeconomic diagnosis is a technique which involves the use of exergy analysis. As a first step towards improving its performance, this work is focused on the thermodynamic and exergy analysis of a direct expansion air conditioning system used in small commercial building applications. The analysis was carried out by means of experimental activities on a 17.5 kW rooftop unit installed at the Herrick Laboratories, Purdue University, Indiana (USA). The system under investigation was equipped with a va…

An Augmented Reality (AR) CAD System at Construction Sites

2011

Augmented Reality (AR) technologies allow computer-generated content to be superimposed over a live camera view of the real world. Although AR is still a very promising technology, currently only a few commercial applications for industrial purposes exploit the potential of adding contextual content to real scenarios. Most of AR applications are oriented to fields such as education or entertainment, where the requirements in terms of repeatability, fault tolerance, reliability and safety are low. Different visualization devices, tracking methods and interaction techniques are described in the literature, establishing a classification between Indoor and Outdoor AR systems. On the one hand, t…

DEMO: Unconventional WiFi-ZigBee communications without gateways

2014

Nowadays, the overcrowding of ISM bands is becoming an evident limitation for the performance and widespread usage of 802.11 and 802.15.4 technologies. In this demo, we prove that it is possible to opportunistically exploit the inter-technology interference between 802.11 and 802.15.4 to build an unconventional low-rate communication channel and signalling protocol, devised to improve the performance of each contending technology. Differently from previous solutions, inter-technology communications do not require the deployment of a gateway with two network interfaces, but can be activated (when needed) directly between two heterogeneous nodes, e.g. a WiFi node and a ZigBee node. This capab…