Radiant cooling/heating technology is energy efficient and can provide excellent thermal comfort ... more Radiant cooling/heating technology is energy efficient and can provide excellent thermal comfort and indoor air quality. This paper studied a residential building to assess its suitability for floor radiant system. The building was proposed to have an architectural membrane like a false ceiling between the ground and first floors. Three air-conditioning systems namely forced air only, hybrid and radiant systems were simulated and compared in CFD to evaluate the indoor air thermal comfort. The results showed radiant floor system offered better thermal comfort. Moreover, the false ceiling effect actually induced temperature stratifications that benefited the ground floor living areas. Compared to the wholly forced air system that circulates air around the entire building, energy savings can be realized from less air volume to condition and consequently less mechanical energy for the motors and fans. For this particular type of application the radiant heating/cooling system was deemed ...
It is logical to consider the use of solar thermal energy to drive a thermally operated cooling s... more It is logical to consider the use of solar thermal energy to drive a thermally operated cooling system because of the excellent temporal match between solar availability and building thermal load. One of the options falling in this category is that of the solar driven thermal jet ejector air conditioning system which unfortunately suffers from a low performance efficiency. Recent studies have concentrated on combining such an ejector system with a more conventional electrically driven vapour compression system to improve the overall system effectiveness. In this paper attention is focused on clarifying the important design parameters for one such system including the selection of the environmentally acceptable single refrigerant working fluid. Future work required is also indicated in terms of system simulation studies.
One-dimensional ejector analyses often use coefficients derived from experimental data for a set ... more One-dimensional ejector analyses often use coefficients derived from experimental data for a set of operating conditions with limited functionality. In this study, several ejector designs were modelled using finite volume CFD techniques to resolve the flow dynamics in the ejectors. The CFD results were validated with available experimental data. Flow field analyses and predictions of ejector performance outside the experimental range were also carried out. During validation, data from CFD predicted the entrainment ratios with greater accuracy on definite area ratios, although no shock was recorded in the ejector. Predictions outside the experimental range-at operating conditions in a combined ejector-vapour compression system-and flow conditions resulting from ejector geometry variations are discussed. It is found that the maximum entrainment ratio happens in the ejector just before a shock occurs and that the position of the nozzle is an important ejector design parameter.
Infiltration is rarely considered a critical factor in AC design. Purposed built buildings such a... more Infiltration is rarely considered a critical factor in AC design. Purposed built buildings such as libraries or shopping centres with dynamic occupants may prove otherwise. The main access to Macquarie University Library is through three large doors in the foyer. Infiltration/exfiltration rates through these doors warranted a careful analysis for its HVAC design and sizing. The Airflow Network model in EnergyPlus was utilised to simulate the bulk air flow throughout the whole building driven by the inflow/outflow through these doors with wind-tunnel-tested wind pressure coefficients. Compared with the model without infiltration modelling, the cooling energy in the foyer exceeds it by almost an order of magnitude and significantly more for heating energy due to sensible heat loss in winter. The infiltration/exfiltration energy component alone made up around 13% of the total annual building AC energy.
The performance of an air distribution system within a room/zone can be rated in terms of ADPI (t... more The performance of an air distribution system within a room/zone can be rated in terms of ADPI (the Air Diffusion Performance Index). Among the several evaluation methods used to design air distribution systems based on flow rate, sound data, isovels and comfort criteria, the ADPI selection method is quite commonly used. The selection process takes advantage of ADPI’s correlation with the ratio of isothermal throw of the diffuser and the characteristic length of the system in the room. This paper clarifies what ADPI is and is not, what is involved in the selection process and how it fares against the industry standards and benchmarks in ventilation and thermal comfort. Several factors that may potentially cause any deviation to the predicted value of ADPI during the design stage are discussed. The post-installation ADPI that reflects the actual ADPI rating for a space has to be assessed and verified on-site. This on-site measurement should be conducted in accordance with a set of gu...
Radiant cooling/heating technology is energy efficient and can provide excellent thermal comfort ... more Radiant cooling/heating technology is energy efficient and can provide excellent thermal comfort and indoor air quality. This paper studied a residential building to assess its suitability for floor radiant system. The building was proposed to have an architectural membrane like a false ceiling between the ground and first floors. Three air-conditioning systems namely forced air only, hybrid and radiant systems were simulated and compared in CFD to evaluate the indoor air thermal comfort. The results showed radiant floor system offered better thermal comfort. Moreover, the false ceiling effect actually induced temperature stratifications that benefited the ground floor living areas. Compared to the wholly forced air system that circulates air around the entire building, energy savings can be realized from less air volume to condition and consequently less mechanical energy for the motors and fans. For this particular type of application the radiant heating/cooling system was deemed ...
It is logical to consider the use of solar thermal energy to drive a thermally operated cooling s... more It is logical to consider the use of solar thermal energy to drive a thermally operated cooling system because of the excellent temporal match between solar availability and building thermal load. One of the options falling in this category is that of the solar driven thermal jet ejector air conditioning system which unfortunately suffers from a low performance efficiency. Recent studies have concentrated on combining such an ejector system with a more conventional electrically driven vapour compression system to improve the overall system effectiveness. In this paper attention is focused on clarifying the important design parameters for one such system including the selection of the environmentally acceptable single refrigerant working fluid. Future work required is also indicated in terms of system simulation studies.
One-dimensional ejector analyses often use coefficients derived from experimental data for a set ... more One-dimensional ejector analyses often use coefficients derived from experimental data for a set of operating conditions with limited functionality. In this study, several ejector designs were modelled using finite volume CFD techniques to resolve the flow dynamics in the ejectors. The CFD results were validated with available experimental data. Flow field analyses and predictions of ejector performance outside the experimental range were also carried out. During validation, data from CFD predicted the entrainment ratios with greater accuracy on definite area ratios, although no shock was recorded in the ejector. Predictions outside the experimental range-at operating conditions in a combined ejector-vapour compression system-and flow conditions resulting from ejector geometry variations are discussed. It is found that the maximum entrainment ratio happens in the ejector just before a shock occurs and that the position of the nozzle is an important ejector design parameter.
Infiltration is rarely considered a critical factor in AC design. Purposed built buildings such a... more Infiltration is rarely considered a critical factor in AC design. Purposed built buildings such as libraries or shopping centres with dynamic occupants may prove otherwise. The main access to Macquarie University Library is through three large doors in the foyer. Infiltration/exfiltration rates through these doors warranted a careful analysis for its HVAC design and sizing. The Airflow Network model in EnergyPlus was utilised to simulate the bulk air flow throughout the whole building driven by the inflow/outflow through these doors with wind-tunnel-tested wind pressure coefficients. Compared with the model without infiltration modelling, the cooling energy in the foyer exceeds it by almost an order of magnitude and significantly more for heating energy due to sensible heat loss in winter. The infiltration/exfiltration energy component alone made up around 13% of the total annual building AC energy.
The performance of an air distribution system within a room/zone can be rated in terms of ADPI (t... more The performance of an air distribution system within a room/zone can be rated in terms of ADPI (the Air Diffusion Performance Index). Among the several evaluation methods used to design air distribution systems based on flow rate, sound data, isovels and comfort criteria, the ADPI selection method is quite commonly used. The selection process takes advantage of ADPI’s correlation with the ratio of isothermal throw of the diffuser and the characteristic length of the system in the room. This paper clarifies what ADPI is and is not, what is involved in the selection process and how it fares against the industry standards and benchmarks in ventilation and thermal comfort. Several factors that may potentially cause any deviation to the predicted value of ADPI during the design stage are discussed. The post-installation ADPI that reflects the actual ADPI rating for a space has to be assessed and verified on-site. This on-site measurement should be conducted in accordance with a set of gu...
Uploads
Papers by Eddy Rusly