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Abstract Virtual product design (VPD) of the refrigeration cycle has long been a major subject of many engineers and manufacturers. Issues should be the question of how simulation gets close to the real world in virtual ways. It is especially true when we consider variable refrigerant flow (VRF) heat pumps, having various types of indoor unit combinations, long and complicated piping configurations, and simultaneous cooling and heating functions under extreme weather conditions. In this regard, model-based systems engineering (MBSE) or model-based design (MBD) guides a methodology to make a virtual model easily. Now, there are plenty of engineering platforms and tools to make a strong simulation model, which provides interfacing technology among multiple physics, different dimensions, and codes in different languages. In the study, the authors share their experience in the virtual design for a VRF heat pump system including the architecture, multiple physics, and the connection with the control SW. Modelica, an acausal and object-oriented modeling language, constructs the backbone of the model to describe the dynamic behavior of refrigerants and to combine external components in the form of functional mock-up units (FMUs). The developed virtual model is validated against measured data, showing it can reproduce all the essential physics of interest both in qualitative and quantitative ways.

It is a considerable challenge to develop a mathematical method for modelling the coupling relationship between the control signal and braking performance in the design and optimization, especially with a highly nonlinear system. The present study thus establishes an integrated CFD-aided method, elaborately proposed based on a 1D/3D co-simulation to accomplish a goal of collaborative calculation between multi-physics fields, and conducting the braking and thermal properties that changes dynamically with the control signal. In particular, the 3D model is actually a multi-domain coupling CFD transient calculation, and the 1D model provides the dynamic boundary conditions. These results manifest some interesting issues, such as modelling the prediction interaction between the isolated control signal and dynamic braking capability. The synergies of the blade agitation and centrifugal force in the multi-phases development affect the oil-filling control and braking generation. The control pressure (Pair) and throttle area (Aout) are predominated in enhancing braking torque, shortening response time, and improving heat dissipation efficiency. The operations of Pair ≤ 3.2 bar and Aout ≥ 64π mm2 ensure a safe and reliable design and then optimize braking and control characteristics. The resulting maximum braking torque is 4070Nm, and the outlet oil temperature is reduced to 138°C.

It is a considerable challenge to develop a mathematical method for modelling the coupling relationship between the control signal and braking performance in the design and optimization, especially with a highly nonlinear system. The present study thus establishes an integrated CFD-aided method, elaborately proposed based on a 1D/3D co-simulation to accomplish a goal of collaborative calculation between multi-physics fields, and conducting the braking and thermal properties that changes dynamically with the control signal. In particular, the 3D model is actually a multi-domain coupling CFD transient calculation, and the 1D model provides the dynamic boundary conditions. These results manifest some interesting issues, such as modelling the prediction interaction between the isolated control signal and dynamic braking capability. The synergies of the blade agitation and centrifugal force in the multi-phases development affect the oil-filling control and braking generation. The control pressure (Pair) and throttle area (Aout) are predominated in enhancing braking torque, shortening response time, and improving heat dissipation efficiency. The operations of Pair ≤ 3.2 bar and Aout ≥ 64π mm2 ensure a safe and reliable design and then optimize braking and control characteristics. The resulting maximum braking torque is 4070Nm, and the outlet oil temperature is reduced to 138°C. [ABSTRACT FROM AUTHOR]

When a heat pipe is used as a cooling system for road vehicles, it is subject to acceleration which can adversely affect its thermal performance. In this study, we investigate the possibility of applying heat pipes for the cooling of power modules subject to time-varying power dissipation and time-dependent acceleration vectors whose projection along the heat pipe axis is up to 3 g. The problem is tackled by modelling the heat pipe through a lumped parameter thermal network (LPTN). A numerical algorithm is used to solve the equations of LPTN representing the heat pipe. The code is then coupled with a 3 D CFD solver (OpenFOAM) to perform a 1D/3D co-simulation and test the applicability of heat pipes as the cooling system in high-performance cars. • Lumped Parameters Thermal Network to simulate heat pipes under acceleration; • 1D/3D co-simulation with OpenFOAM to study power module temperature distribution; • Investigation, through an application, of the effect of accelerations on the thermal performance of heat pipes. [ABSTRACT FROM AUTHOR]

This paper investigates a co-simulation approach through which one dimensional (1D) system simulation model of aircraft environmental control system (ECS) and three dimensional (3D) CFD model of cabin are coupled together, data exchange between typical 1D system simulation program AMESim and 3D Computational Fluid Dynamics(CFD) program Fluent is completed with a developed co-simulation interface. With 1D system model of ECS and 3D CFD model of cabin built in AMESim and Fluent respectively, this paper investigates the transient temperature distribution in aircraft cabin to demonstrate the effectiveness of 1D/3D co-simulation approach, a comparison of temperature distribution calculation result between 1D/3D cosimulation and standalone 1D system simulation is fulfilled, the result indicates an obvious temperature stratification in cabin and the co-simulation method can provide more detailed information than standalone 1D system simulation. Great benefit of 1D/3D cosimulation is proved to make 1D system simulation and 3D CFD become complementary. [ABSTRACT FROM AUTHOR]

• Different 1D/3D co-simulation implementation strategies within the CFD industry were identified. • Four different 1D/3D co-simulation strategies were explored to investigate the radiative- and convective heat transfer, and natural circulation phenomena occurring in a simplified water cooled RCCS facility. • The impact on simulation – stability, time and results were investigated. • The 1D/3D co-simulation methodologies were compared to a full 1D model consisting of the same specifications and setup. 1D/3D co-simulation is a promising approach for the modelling and simulation of complex systems. These systems are typically computationally intensive. By combining the desired features of a one-dimensional (1D) systems code and a three-dimensional (3D) Computational Fluid Dynamics (CFD) code, the required resources are optimized whilst still retaining an acceptable level of accuracy. Co-simulation has been applied in various domains and scenarios, often without a comprehensive study on the impact to simulation- stability, -time, and results. The purpose of this study is to explore the behaviour of some of the strategies by applying them to the simulation of the natural circulation occurring in a simplified Reactor Cavity Cooling System (RCCS). Four different co-simulation approaches were explored to investigate the radiative- and convective- heat transfer as well as the natural circulation phenomena occurring in a RCCS facility. Typically, in these four modelling approaches a 3D methodology was employed to model the radiation and convection heat transfer in the cavity between the heater wall and the outer wall of the riser. The 1D methodology was employed to model the remainder of the RCCS system. The 1D systems code, Flownex, and the 3D CFD code Ansys Fluent were used to perform the 1D/3D co-simulations. Each of the codes modelled a relevant part of the RCCS facility and the models were coupled by explicitly exchanging boundary conditions or relevant data between the 1D and 3D regions. The validity of the coupled 1D/3D approaches was investigated by comparing them with a full 1D simulation. [ABSTRACT FROM AUTHOR]