scholarly journals Thermal - electrical analogy in dynamic simulations of buildings: Comparison of four numerical solution methods

2020 ◽  
Vol 4 (2) ◽  
pp. 179-188
Author(s):  
Piotr Michalak
Keyword(s):  
Dynamic Modelling ◽  
Computation Method ◽  
Test Cases ◽  
Dynamic Simulations ◽  
Transient Behaviour ◽  
Heating And Cooling ◽  
Capacitance Method ◽  
Numerical Solution Methods ◽  
Electrical Analogy ◽  
Solution Methods

The lumped capacitance method is widely used in dynamic modelling of buildings. Models differ in complexity, solution methods and ability to simulate transient behaviour of described objects. The paper presents a mathematical description of a simple 1R1C thermal network model of a building zone. Four numerical methods were applied to solve differential equation describing its dynamics. For validation purposes two test cases (600 and 900) from the BESTEST procedure were used. In both cases detailed results were given. Better ability of the simulation model to reproduce transient behaviour of the modelled buildings was noticed in case of the lightweight object (case 600). Annual heating and cooling demand was within the reference range for heavyweight one (case 900). The kind of the computation method had no significant effect on simulation results.

scholarly journals Numerical Evaluation of a HVAC System Based on a High-Performance Heat Transfer Fluid

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3298
Author(s):  
Gianpiero Colangelo ◽  
Brenda Raho ◽  
Marco Milanese ◽  
Arturo de Risi
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Cooling System ◽  
Electrical Energy ◽  
Simulation Software ◽  
Heat Transfer Fluid ◽  
Hvac System ◽  
Dynamic Simulations ◽  
Heating And Cooling ◽  
The University

Nanofluids have great potential to improve the heat transfer properties of liquids, as demonstrated by recent studies. This paper presents a novel idea of utilizing nanofluid. It analyzes the performance of a HVAC (Heating Ventilation Air Conditioning) system using a high-performance heat transfer fluid (water-glycol nanofluid with nanoparticles of Al2O3), in the university campus of Lecce, Italy. The work describes the dynamic model of the building and its heating and cooling system, realized through the simulation software TRNSYS 17. The use of heat transfer fluid inseminated by nanoparticles in a real HVAC system is an innovative application that is difficult to find in the scientific literature so far. This work focuses on comparing the efficiency of the system working with a traditional water-glycol mixture with the same system that uses Al2O3-nanofluid. The results obtained by means of the dynamic simulations have confirmed what theoretically assumed, indicating the working conditions of the HVAC system that lead to lower operating costs and higher COP and EER, guaranteeing the optimal conditions of thermo-hygrometric comfort inside the building. Finally, the results showed that the use of a nanofluid based on water-glycol mixture and alumina increases the efficiency about 10% and at the same time reduces the electrical energy consumption of the HVAC system.

An Investigation Into the Compliance of SCARA Robots. Part II: Experimental and Numerical Validation

1988 ◽  
Vol 110 (1) ◽  
pp. 23-30 ◽  
Author(s):  
H. A. ElMaraghy ◽  
B. Johns
Keyword(s):  
Elastic Compliance ◽  
Servo Control ◽  
Compliance Matrix ◽  
End Effector ◽  
Prismatic Parts ◽  
Numerical Solution Methods ◽  
Solution Methods ◽  
Using Data ◽  
Assembly Performance ◽  
Robot Configurations

A model of inherent elastic compliance was developed for general position-controlled SCARA, with conventional joint feedback control, for both rotational and prismatic part insertion (Part I). The developed model was applied to the SKILAM and ADEPT I robots for validation. Experimental procedures and numerical solution methods are described. It was found that the ADEPT I robot employs a coupled control strategy between joints one and two which produces a constant, decoupled end effector compliance. The applicable compliance matrix, in this case, is presented and the experimental results are discussed. The model may be used to develop compliance maps that define the amount of end effector compliance, as a function of the joints compliance, as well as its variation for different robot configurations. This is illustrated using data for the SKILAM SCARA robot. Results are plotted and discussed. The most appropriate robot postures for assembly were found for both rotational and prismatic parts. The conditions necessary to achieve compliance or semicompliance centers with the SKILAM robot were examined. The results and methods demonstrated in these examples may be used to select appropriate robots for given applications. They can also guide robot designers in selecting joint servo-control gains to obtain the desired joints compliance ratio and improve assembly performance.

Dynamic Modelling and Experimental Validation of a Domestic Refrigeration Cycle

2021 ◽  
pp. 1-33
Author(s):  
Akin Caglayan ◽  
Salman Mustafa Husain ◽  
Mutlu Ipek ◽  
Tolga Nurettin Aynur ◽  
Sertac Cadirci
Keyword(s):  
Capillary Tube ◽  
Dynamic Modelling ◽  
Object Oriented Programming ◽  
Condensation Temperature ◽  
Refrigeration Cycle ◽  
Transient Behaviour ◽  
Analysis And Design ◽  
Cyclic Behaviour ◽  
Suction Line Heat Exchanger ◽  
Tube Suction

Abstract Performance analysis and design optimization of refrigerators are primarily carried out by time-consuming experiments. The current study presents an alternative method of analysing refrigerators through modelling of the cooling cycle using a software called Dymola, based on an object-oriented programming language, called Modelica. The main components of a domestic refrigerator (compressor, condenser, evaporator, cabinet and capillary tube-suction-line heat exchanger) are first modelled and validated individually. The full dynamic refrigeration cycle model is created afterwards. Both the simulations and the experiments have been conducted using R600a as the refrigerant with on-and off-modes of the reciprocating, single speed compressor. To represent the dynamic cyclic behaviour of the refrigerator, an algorithm block is also included. The algorithm controls the operation using two set-point temperatures of the cabinet. Experiments have been carried out on a single door refrigerator having an interior volume of 343 litres for the validation of the one-dimensional dynamic model. Results show that the cabinet air, evaporation temperature, condensation temperature, power and energy values deviate from experimental values by less than 2°C and 2% respectively. The dynamic modelling is found to be in good agreement with the experiments in the on mode of the compressor and a promising and rapid tool to represent the transient behaviour of the refrigerator.

Blade Fault Recognition Based on Signal Processing and Adaptive Fluid Dynamic Modelling

1997 ◽  
Author(s):  
A. Stamatis ◽  
N. Aretakis ◽  
K. Mathioudakis
Keyword(s):  
Flow Field ◽  
Fluid Dynamic ◽  
Measurement Data ◽  
Dynamic Modelling ◽  
Physical Modelling ◽  
Diagnostic Procedures ◽  
Measured Quantity ◽  
Test Cases ◽  
Actual Measurement ◽  
Fault Recognition

An approach for identification of faults in blades of a gas turbine, based on physical modelling is presented. A measured quantity is used as an input and the deformed blading configuration is produced as an output. This is achieved without using any kind of “signature”, as is customary in diagnostic procedures for this kind of faults. A fluid dynamic model is used in a manner similar to what is known as “inverse design methods”: the solid boundaries which produce a certain flow field are calculated by prescribing this flow field. In the present case a signal, corresponding to the pressure variation on the blade-to-blade plane, is measured. The blade cascade geometry that has produced this signal is then produced by the method. In the paper the method is described and applications to test cases are presented. The test cases include theoretically produced faults as well as experimental cases, where actual measurement data are shown to produce the geometrical deformations which existed in the test engine.

Nonequilibrium Continuum Traffic Flow Model with Frozen Sound Wave Speed

2003 ◽  
Vol 1852 (1) ◽  
pp. 183-192
Author(s):  
W. L. Jin ◽  
H. M. Zhang
Keyword(s):  
Traffic Flow ◽  
Sound Speed ◽  
Flow Model ◽  
Wave Model ◽  
Homogeneous System ◽  
Traffic Flow Model ◽  
Traffic Conditions ◽  
Numerical Solution Methods ◽  
Stable Conditions ◽  
Solution Methods

Results are presented from a recent study on a variation of a new non-equilibrium continuum traffic flow model in which traffic sound speed is constant. Hence this model is called the frozen-wave model. This model resembles the Payne–Whitham model but avoids the “back-traveling” of the latter. For this frozen-wave model, the Riemann problem is analyzed for its homogeneous system, two numerical solution methods are developed to solve it, and numerical simulations are carried out under both stable and unstable traffic conditions. These results show that under stable conditions, the model behaves similarly to the Payne–Whitham model. However, under unstable traffic conditions, it has nonphysical solutions or no solutions when a vacuum problem occurs. This study, on the one hand, provides a more complete picture of the properties of this frozen-wave model and reduces the risk of improper applications of it. On the other hand, it also highlights the need to adopt a density-dependent sound speed.

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