The paper presents a new method to determine the sensible effectiveness and pressure loss of rotary regenerative heat exchangers using computational fluid dynamics(CFD).It is based on CFD simulations of a single therm...The paper presents a new method to determine the sensible effectiveness and pressure loss of rotary regenerative heat exchangers using computational fluid dynamics(CFD).It is based on CFD simulations of a single thermal wheel microchannel with a small cross-sectional area and thin walls,with cyclic inlet and outlet boundary conditions.Two unique measurement set-ups were designed and built for the experimental measurement of the heat exchanger characteristics.Five different types of thermal wheels were manufactured,measured,and simulated in ANSYS Fluent.All wheels achieve an effectiveness greater than 73%under certain(air flow)conditions,which is the minimum effectiveness required by Ecodesign(in the EU).For the examined exchangers,the effectiveness ranges from 66.5%to 83.3%,depending on the boundary conditions and geometric parameters of the rotors.The highest sensible effectiveness is achieved by heat exchangers with the largest heat exchange surface Ac;on the other hand,these wheels have the largest pressure loss.The paper discusses the use of a simplifiedε-NTU correlation model for the HVAC systems(typically C*=1).The correlation model and CFD results were compared and found to be different from each other.The results of the CFD simulation were compared with measurements to prove that the proposed simulation method can predict the behaviour of the real heat exchanger as a whole.It was demonstrated that the sensible effectiveness and pressure loss of the rotary heat exchanger predicted by the CFD simulations correspond well to the measured values within the measurement uncertainty±1.3%.The proposed method can be used for the comparison of different rotary regenerative heat exchangers before their manufacturing and for verification that they meet the EU Ecodesign requirements set by the current legislation.It reduces the cost of the initial optimisation and testing of new designs.展开更多
Insufficient fresh air supply due to the increased air tightness of building envelopes after building renovations and window upgrades is a major concern of HVAC engineering today.The paper demonstrates the application...Insufficient fresh air supply due to the increased air tightness of building envelopes after building renovations and window upgrades is a major concern of HVAC engineering today.The paper demonstrates the application of CFD simulations in the development of a compact decentralised ventilation unit with integrated heat recovery system for local ventilation of rooms,targeting this common issue.The device houses an innovative cyclically rotating recuperative heat exchanger,allowing effective condensate removal and de-icing in winter for its independent operation throughout the year.The paper introduces the ventilation unit,describes preparation of its numerical models,and conducts CFD simulation using Ansys Fluent software.The initial design of the device was improved following the findings of the numerical analysis,and the proposed adjustments were tested through follow-up CFD simulations,confirming that the desired outcomes were achieved.A separate CFD analysis was performed to assess the use of different air supply elements at the air outlet to the room,recommending the use of adjustable nozzles.A prototype ventilation unit was manufactured and the volume flow rate under different operating conditions was measured to be compared with the simulation results.The outcome of the research is a new type of compact local ventilation unit.An increase in device energy efficiency was achieved,with the aid of simulations,while maintaining its compact size.In addition to presenting the potential of using variant CFD analysis in the development of new HVAC equipment,the paper also indicates the drawbacks of using the Multiple Reference Frame(MRF)method to approximate the rotation of radial fan impellers in CFD simulations.展开更多
文摘The paper presents a new method to determine the sensible effectiveness and pressure loss of rotary regenerative heat exchangers using computational fluid dynamics(CFD).It is based on CFD simulations of a single thermal wheel microchannel with a small cross-sectional area and thin walls,with cyclic inlet and outlet boundary conditions.Two unique measurement set-ups were designed and built for the experimental measurement of the heat exchanger characteristics.Five different types of thermal wheels were manufactured,measured,and simulated in ANSYS Fluent.All wheels achieve an effectiveness greater than 73%under certain(air flow)conditions,which is the minimum effectiveness required by Ecodesign(in the EU).For the examined exchangers,the effectiveness ranges from 66.5%to 83.3%,depending on the boundary conditions and geometric parameters of the rotors.The highest sensible effectiveness is achieved by heat exchangers with the largest heat exchange surface Ac;on the other hand,these wheels have the largest pressure loss.The paper discusses the use of a simplifiedε-NTU correlation model for the HVAC systems(typically C*=1).The correlation model and CFD results were compared and found to be different from each other.The results of the CFD simulation were compared with measurements to prove that the proposed simulation method can predict the behaviour of the real heat exchanger as a whole.It was demonstrated that the sensible effectiveness and pressure loss of the rotary heat exchanger predicted by the CFD simulations correspond well to the measured values within the measurement uncertainty±1.3%.The proposed method can be used for the comparison of different rotary regenerative heat exchangers before their manufacturing and for verification that they meet the EU Ecodesign requirements set by the current legislation.It reduces the cost of the initial optimisation and testing of new designs.
文摘Insufficient fresh air supply due to the increased air tightness of building envelopes after building renovations and window upgrades is a major concern of HVAC engineering today.The paper demonstrates the application of CFD simulations in the development of a compact decentralised ventilation unit with integrated heat recovery system for local ventilation of rooms,targeting this common issue.The device houses an innovative cyclically rotating recuperative heat exchanger,allowing effective condensate removal and de-icing in winter for its independent operation throughout the year.The paper introduces the ventilation unit,describes preparation of its numerical models,and conducts CFD simulation using Ansys Fluent software.The initial design of the device was improved following the findings of the numerical analysis,and the proposed adjustments were tested through follow-up CFD simulations,confirming that the desired outcomes were achieved.A separate CFD analysis was performed to assess the use of different air supply elements at the air outlet to the room,recommending the use of adjustable nozzles.A prototype ventilation unit was manufactured and the volume flow rate under different operating conditions was measured to be compared with the simulation results.The outcome of the research is a new type of compact local ventilation unit.An increase in device energy efficiency was achieved,with the aid of simulations,while maintaining its compact size.In addition to presenting the potential of using variant CFD analysis in the development of new HVAC equipment,the paper also indicates the drawbacks of using the Multiple Reference Frame(MRF)method to approximate the rotation of radial fan impellers in CFD simulations.
