16 research outputs found
Modelling and intelligent control of vehicle climatronic systems
The modelling and control method of a vehicle climatronic system, based on MATLAB/SIMULINK, is presented. In order to achieve high modelling accuracy, a developed simulation model library is introduced. The modelling approach is described and the developed models are validated with some of experimental data obtained. The models are nonlinear, independent of fluid type and based on thermo-dynamic principles. Analysis of the cooling circuit modelling and empirical real-time control models are created by using Fuzzy logic controller and Stateflow. Both of control input and output are implemented essentially at original vehicle CAN-Bus system. Feasible digital automatic control strategy basic to fuzzy theory, hardware and software solution are given. The simulation experiment is achieved with the Hardware-in-Loop technology. This control methodology is easily operated and worth applying for any further studies or methods
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Measurements and modelling of a novel oil-free refrigeration system
Vapour compression refrigeration (VCR) system is one of the most commonly used refrigeration methods for domestic refrigeration, heat pump, and automobile air conditioning. The ever rapid rise in the number of VCR units causes a dramatic increase in energy demand and greenhouse emissions, which results in a significant contribution to the global warming. To mitigate the greenhouse gas emission and improve energy efficiency, high efficiency and low carbon oil-free refrigeration system with capacity modulation can be considered as a potential solution for VCR units. A novel oil-free refrigeration system (ORS) is introduced in this thesis. The performance of the ORS has been experimentally and numerically investigated.
The ORS consisting of two balanced novel oil-free linear compressors, an off-the-shelf water-cooled coaxial condenser and an evaporator with an electric heater has been instrumented. A series of experiments have been carried out over a wide range of test conditions to investigate the performance of the linear compressor using R134a. At a compressor stroke of 11 mm and a pressure ratio of 2.0, the oil-free linear compressor can achieve a volumetric efficiency of 71%. The oil-free linear compressor is capable of capacity modulation in response to heat load. Part load efficiency is even higher. An analytical model of the linear compressor has been developed.
The drop-in performance of R1234yf for R134a system also has been experimentally investigated using the ORS test rig. At a condenser temperature of 40 °C, the coefficient of performance (CoP) of R1234yf is 5-20% lower than R134a.
The effect of the refrigerant charge and refrigerant distribution for the ORS using R134a has been experimentally evaluated. The experimental results show that an optimal refrigerant charge, which allows the system to achieve the highest efficiency, varies with operating conditions. A higher compressor stroke and a lower pressure ratio tend to have a higher optimal refrigerant charge.
To provide the numerical ORS model with evaporation heat transfer and pressure drop of refrigerants, two existing correlations for heat transfer and pressure drop for R1234yf, R152a and R134a have been improved based on the experimental data. Overall, the modelling results agree well with the measurements.
A comprehensive numerical system model for the ORS consisting of linear compressor model, a heat exchanger model, and a refrigerant distribution model has been proposed using MATLAB and Simulink. The model is able to predict mass flow rate, power input, pressure drop and heat transfer in heat exchangers, and CoP of the refrigeration system. Overall, the modelling results agree well with measurements. The numerical model can be used for future work on low charge ORS design using oil-free linear compressor and microchannel heat exchangers for various applications
Advances in Condition Monitoring, Optimization and Control for Complex Industrial Processes
The book documents 25 papers collected from the Special Issue “Advances in Condition Monitoring, Optimization and Control for Complex Industrial Processes”, highlighting recent research trends in complex industrial processes. The book aims to stimulate the research field and be of benefit to readers from both academic institutes and industrial sectors
TRANSIENT MODELING OF TWO-STAGE AND VARIABLE REFRIGERANT FLOW VAPOR COMPRESSION SYSTEMS WITH FROSTING AND DEFROSTING
This thesis presents the development of an advanced modeling framework for the transient simulation of vapor compression systems. This framework contains a wide range of components and its modular nature enables an arbitrary cycle configuration to be analyzed. One of the highlights of this framework is the first-principles heat exchanger models with many salient simulation capabilities. Specifically, a high-order discretized model employing finite volume analysis is developed based on a decoupled approach to modeling the heat transfer and pressure drop performance of the heat exchanger. The frosting and defrosting models developed in the thesis are integrated into this heat exchanger model, allowing more accurate performance assessment of heat pumps. Meanwhile, an advanced low-order moving boundary heat exchanger model is developed with switched model representations to accommodate the changing numbers of fluid zones under large disturbances. Compared to the existing moving boundary models in the literature, this new model accounts for refrigerant pressure drop and possesses a more accurate evaluation for the air side heat transfer.
Based on this modeling framework, the transient characteristics of a flash tank vapor injection (FTVI) heat pump system undergoing cycling, frosting and reverse-cycle defrosting operations are thoroughly explored. The dynamic system response when subjected to a step change in the opening of the upper-stage electronic expansion valve is also investigated. Comparison between the predictions and experimental data shows that the simulation can adequately capture the transient heat transfer and fluid flow phenomena of the system and thus demonstrating the fidelity of the models. Furthermore, a pull-down simulation for a multi-split variable refrigerant flow (VRF) air-conditioning system with six indoor units has been carried out. Control strategy that aims to maintain the indoor air temperatures at set values is proposed. The simulation test for controllability shows that the proposed control strategy is feasible to achieve the temperature control of individual zones
A Predictive maintenance model for heterogeneous industrial refrigeration systems
The automatic assessment of the degradation state of industrial refrigeration systems is
becoming increasingly important and constitutes a key-role within predictive maintenance
approaches. Lately, data-driven methods especially became the focus of research in this
respect. As they only rely on historical data in the development phase, they offer great
advantages in terms of flexibility and generalisability by circumventing the need for specific
domain knowledge. While most scientific contributions employ methods emerging from
the field of machine learning (ML), only very few consider their applicability amongst
different heterogeneous systems. In fact, the majority of existing contributions in this field
solely apply supervised ML models, which assume the availability of labelled fault data for
each system respectively. However, this places restrictions on the overall applicability, as
data labelling is mostly conducted by humans and therefore constitutes a non-negligible
cost and time factor. Moreover, such methods assume that all considered fault types
occurred in the past, a condition that may not always be guaranteed to be satisfied.
Therefore, this dissertation proposes a predictive maintenance model for industrial
refrigeration systems by especially addressing its transferability onto different but related heterogeneous systems. In particular, it aims at solving a sub-problem known as
condition-based maintenance (CBM) to automatically assess the system’s state of degradation. To this end, the model does not only estimate how far a possible malfunction
has progressed, but also determines the fault type being present. As will be described
in greater detail throughout this dissertation, the proposed model also utilises techniques
from the field of ML but rather bypasses the strict assumptions accompanying supervised
ML. Accordingly, it assumes the data of the target system to be primarily unlabelled
while a few labelled samples are expected to be retrievable from the fault-free operational
state, which can be obtained at low cost. Yet, to enable the model’s intended functionality, it additionally employs data from only one fully labelled source dataset and, thus,
allows the benefits of data-driven approaches towards predictive maintenance to be further
exploited.
After the introduction, the dissertation at hand introduces the related concepts as
well as the terms and definitions and delimits this work from other fields of research.
Furthermore, the scope of application is further introduced and the latest scientific work
is presented. This is then followed by the explanation of the open research gap, from which
the research questions are derived. The third chapter deals with the main principles of the
model, including the mathematical notations and the individual concepts. It furthermore
delivers an overview about the variety of problems arising in this context and presents the
associated solutions from a theoretical point of view. Subsequently, the data acquisition
phase is described, addressing both the data collection procedure and the outcome of the
test cases. In addition, the considered fault characteristics are presented and compared
with the ones obtained from the related publicly available dataset. In essence, both
datasets form the basis for the model validation, as discussed in the following chapter. This
chapter then further comprises the results obtained from the model, which are compared
with the ones retrieved from several baseline models derived from the literature. This
work then closes with a summary and the conclusions drawn from the model results.
Lastly, an outlook of the presented dissertation is provide
Proceedings of the First International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics
1st International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Kruger Park, 8-10 April 2002.This lecture is a principle-based review of a growing body
of fundamental work stimulated by multiple opportunities to
optimize geometric form (shape, structure, configuration,
rhythm, topology, architecture, geography) in systems for heat
and fluid flow. Currents flow against resistances, and by
generating entropy (irreversibility) they force the system global
performance to levels lower than the theoretical limit. The
system design is destined to remain imperfect because of
constraints (finite sizes, costs, times). Improvements can be
achieved by properly balancing the resistances, i.e., by spreading
the imperfections through the system. Optimal spreading means
to endow the system with geometric form. The system
construction springs out of the constrained maximization of
global performance. This 'constructal' design principle is
reviewed by highlighting applications from heat transfer
engineering. Several examples illustrate the optimized internal
structure of convection cooled packages of electronics. The
origin of optimal geometric features lies in the global effort to
use every volume element to the maximum, i.e., to pack the
element not only with the most heat generating components, but
also with the most flow, in such a way that every fluid packet is
effectively engaged in cooling. In flows that connect a point to
a volume or an area, the resulting structure is a tree with high conductivity
branches and low-conductivity interstices.tm201
SPATIAL TRANSFORMATION PATTERN DUE TO COMMERCIAL ACTIVITY IN KAMPONG HOUSE
ABSTRACT Kampung houses are houses in kampung area of the city. Kampung House oftenly transformed into others use as urban dynamics. One of the transfomation is related to the commercial activities addition by the house owner. It make house with full private space become into mixused house with more public spaces or completely changed into full public commercial building. This study investigate the spatial transformation pattern of the kampung houses due to their commercial activities addition. Site observations, interviews and questionnaires were performed to study the spatial transformation. This study found that in kampung houses, the spatial transformation pattern was depend on type of commercial activities and owner perceptions, and there are several steps of the spatial transformation related the commercial activity addition.
Keywords: spatial transformation pattern; commercial activity; owner perception, kampung house; adaptabilit