Study on Gas Leakage Detection and Pressure Difference Identification by Asymmetric Differential Pressure Method

As the most common actuator in the pneumatic system, the excellent air tightness of the tank is the key to meet the use requirements of automatic equipment. This paper introduces the common air tightness detection contents, and models the inflation and detection process of the differential pressure method. In order to break away from the restriction on the detection efficiency caused by the asynchronous temperature recovery of the two chambers in the asymmetric differential pressure method, the differential calculation of directly detected pressure difference is replaced by the pressure difference substitute formula. The influence of various parameters in the fitting formula is analyzed by simulation, and the effectiveness of this method is verified by experiments.

Design of Low-Pressure Sand Casting Process for Water-Cooled Motor Shell in Electric Vehicle

Aluminium alloy motor shell is the core part of the new energy vehicle powertrain. It has a complex structure with an average wall thickness of 4∼5mm, a side wall with 6∼7mm spiral water jacket, and the bottom of the shell inlaid with cast steel bearing bushing. Because of its complex structure characteristics, as well as higher internal quality requirements and air tightness requirements, the casting process of motor housing is very difficult. This paper introduces the structural characteristics and common casting defects of the motor shell. On this basis, the typical casting process scheme of motor shell with sand core casting technology and the application of computer simulation technology in the development of motor shell casting process are discussed and shared.

Exterior Wood-Frame Walls—Wind–Vapour Barrier Ratio in Denmark

Wood-frame walls in cold climates are traditional constructed with a vapour barrier that also constitutes the air-tightness layer. Polyethylene foil as a vapour barrier is likely used; however, other building materials can be used to obtain correspondingly sufficient properties. 1D hygrothermal simulations were conducted for a wood-frame structure to investigate the wind–vapour barrier ratio, and if the vapour barrier of polyethylene foil could be omitted and replaced by other materials. The results were postprocessed using the VTT mould model. The results showed how wood-frame walls can be designed with respect to internal humidity class and diffusion resistance divided into three categories: no risk for mould growth, needs further investigation, and is not performing well as the risk for mould growth is present. For internal humidity classes 1–3, the ratio between wind and vapour barrier must be about 1:5, and 1:10 for classes 4 and 5 to be on the safe side. Simulations were performed for the climate of Lund, Sweden, which were used to simulate climate in Denmark too. Nevertheless, the results are related to climate data and, thus, the location.

ON GAS AND HYDRAULIC TIGHTNESS OF LINAC ACCELERATING SECTIONS

A technique for calculating the required impenetrability of brazing linac accelerating sections cooled by water and for control of their hydraulic tightness based on the total helium leakage rate is given. Three types of cooling systems: a water stream in tubes soldered on the outer surface of the sections, a water stream along the outer surface and along the internal cooling channels in sections are considered. It is shown that the contact of accelerating sections surface with cooling water requires increasing the tightness of their soldering at least by 66 times. As an example, requirements for hydraulic and air tightness of accelerating sections for the developed accelerator LU-10 NSC KIPT are given.

Quantifying air leakage through party walls in Toronto semidetached and row-home dwellings

This study contributes to the development of quantifying and understanding building air tightness as it relates to Toronto semi-detached and row homes, particularly party walls. While infiltration characteristics of single family detached homes have been widely developed and understood, the isolation of semi-detached and row home single family dwelling units is relatively unexplored. When quantifying air leakage in a building attached to an adjacent dwelling unit, air is drawn through the exterior envelope as well as the party wall (i.e. shared common wall). The purpose of the proposed testing method, guarded blower door testing, is to isolate air leakage through the party wall from the envelope. Currently the party wall is considered a fire-rated assembly but is not part of the air barrier system. Issues associated with party wall air leakage include spread of fire, indoor air quality, transfer of tobacco smoke between dwellings, and heat loss through the party to attic detail. Data collected on buildings constructed between 1890 and 1920 (Century buildings) has been compared to the data collected on buildings constructed between 2012 to 2017 (new buildings). Air leakage has been collected on twenty-six of Century semi-detached homes with solid masonry construction and twenty-one new semi-detached/row homes of lightweight wood frame construction. Each unit was tested independently and simultaneously, or “guarded”, with the adjacent unit, to pressure neutralize allowing for quantification of envelope and party wall air leakage. Party wall leakage was found to be similar to leakage through the exterior walls. The leakage accounted for 22% of the total infiltration in Century old buildings and 38% in Modern dwellings.

Quantifying air leakage through party walls in Toronto semidetached and row-home dwellings

This study contributes to the development of quantifying and understanding building air tightness as it relates to Toronto semi-detached and row homes, particularly party walls. While infiltration characteristics of single family detached homes have been widely developed and understood, the isolation of semi-detached and row home single family dwelling units is relatively unexplored. When quantifying air leakage in a building attached to an adjacent dwelling unit, air is drawn through the exterior envelope as well as the party wall (i.e. shared common wall). The purpose of the proposed testing method, guarded blower door testing, is to isolate air leakage through the party wall from the envelope. Currently the party wall is considered a fire-rated assembly but is not part of the air barrier system. Issues associated with party wall air leakage include spread of fire, indoor air quality, transfer of tobacco smoke between dwellings, and heat loss through the party to attic detail. Data collected on buildings constructed between 1890 and 1920 (Century buildings) has been compared to the data collected on buildings constructed between 2012 to 2017 (new buildings). Air leakage has been collected on twenty-six of Century semi-detached homes with solid masonry construction and twenty-one new semi-detached/row homes of lightweight wood frame construction. Each unit was tested independently and simultaneously, or “guarded”, with the adjacent unit, to pressure neutralize allowing for quantification of envelope and party wall air leakage. Party wall leakage was found to be similar to leakage through the exterior walls. The leakage accounted for 22% of the total infiltration in Century old buildings and 38% in Modern dwellings.

Impact of a compartmentalization and ventilation system retrofit strategy on energy use in high-rise residential buildings

A compartmentalization and in-suite ventilation system (ISVS) retrofit strategy was investigated for an existing high-rise residential building in Vancouver. Computer simulation using EnergyPlus™ was used to examine the impact of the proposed retrofit on heating energy and GHG emissions for the building’s original 1983 condition, and its current condition which incorporates a 2012 enclosure retrofit. Results show annual heating energy decreased by 51% and overall GHG emissions decreased by 29% for the proposed retrofit applied to the building in its current condition. When applied to the building in its original condition, heating energy decreased by 49% and overall GHG emissions decreased by 21%. The main benefit of the proposed retrofit, however, is improved effectiveness of the mechanical ventilation system. Because building enclosure air-tightness improvements can negatively impact air distribution in buildings with pressurized corridor ventilation systems, the proposed retrofit should be applied in combination with, or before, an enclosure retrofit.