Gas heater

About: Gas heater is a(n) research topic. Over the lifetime, 1799 publication(s) have been published within this topic receiving 6169 citation(s).

Risk factors for contamination of domestic hot water systems by legionellae.

Abstract: To assess risk factors associated with the contamination of the domestic environment by legionellae, 211 houses in the Quebec City area were randomly selected and water samples were collected from the hot water tank, the shower heads, and the most frequently used faucet. After centrifugation, concentrated samples were seeded in triplicate on BCYE and GPV media. Data on the characteristics of the hot water system and plumbing in the house and on the personal habits of the occupants were collected for each house. Among these 211 houses, hot water was provided by either an oil or gas heater in 33 and by an electric heater in 178. Legionellae were isolated from none of the samples from houses with oil or gas heaters and from 39% (69 of 178) of those with electric water heaters (P less than 0.0001). This association remained highly significant after control for water temperature and other variables in a stratified analysis. In the 178 houses with an electric heater, 12% of the faucets, 15% of the shower heads, and 37% of the water heaters were contaminated. Legionella pneumophila serogroups 2 and 4 were the most frequently isolated strains. Logistic regression showed that factors associated with electric water heater contamination were (i) location of the house in older districts of the city (P less than 0.0001), (ii) old age of the water heater (P = 0.003), and (iii) low water temperature (P = 0.05). Contamination of the water heater was the only factor significantly associated with the contamination of peripheral outlets (P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

The laser-assisted cold spray process and deposit characterisation

Abstract: Laser-assisted Cold Spray (LCS) is a new coating and fabrication process which combines the supersonic powder beam found in Cold Spray (CS) with laser heating of the deposition zone. LCS combines some advantages of CS: solid-state deposition, high build rate and the ability to deposit metals onto a range of substrates, with reduced operating costs which arise from not using a gas heater and replacing helium with nitrogen as the process gas. A system has been developed to impact metallic powder particles onto a substrate which is locally heated using a diode laser. A pyrometer and control system are used to record and maintain impact site temperature. In this study,

Gas heater with alarm system

Abstract: A heater including a housing, a heating assembly having a burner, and at least one of an oxygen level detection assembly adapted to distinguish between a relatively normal oxygen level, a relatively low oxygen level and relatively unsafe oxygen, a carbon monoxide sensor and a combustible gas sensor. The heater may also include an indicator adapted to produce at least one of an audible indication and a visible indication in response to a detection of a relatively low oxygen level, a detection of a predetermined level of carbon monoxide, or a detection of combustible gas.

Deposition efficiency, mechanical properties and coating roughness in cold-sprayed titanium

Abstract: In the cold-spray process, metal powder particles develop into a coating as a result of ballistic impingment on a substrate. In cold-spray, compressed gas (air, nitrogen or helium), at pressures ranging between 1.4– 3.4 MPa (200–500 psi), but typically around 1.7 MPa (250 psi), flows through a manifold system containing a gas heater and a powder feeder. The pressurized gas is heated electrically to around 100–600 ◦C then passed through a Laval-type converging/diverging nozzle until the gas velocities reach supersonic speeds. The powder particles are introduced into the gas stream just in front of the converging section of the nozzle and are accelerated by the expanding gas. The powder feedstock is delivered on the high-pressure side of the nozzle by the metering device, which is heated and maintained at the elevated pressure of the manifold. During the supersonic expansion through the Laval nozzle, there is a temperature reduction. Thus, the temperature of the gas stream is always below the melting point of the particulate material, providing coatings developed primarily from particles in the solid state with very little oxidation [1–5]. As cold-spray is a 100% solid-state process, the deposition “in air” of titanium coatings without significant oxidation represent an important technical achievement. Titanium and its alloys are employed in corrosive environments, aerospace and bio-implants [6]. Beyond the solid-state characteristic, a fundamental feature of the cold-spray method is the concept of critical velocity (V ∗). For each coating and substrate combination there is a V ∗. Above the V ∗ the particles will have enough kinetic energy to be incorporated into a coating. Below the V ∗, the particles will be either reflected from the surface (bounced-off) or cause erosion of the substrate and any coating buildup which had begun. For particle velocities V > V ∗, the coating process occurs and the deposition efficiency is seen to increase with increasing V [1, 4, 5]. The actual mechanisms by which the solid-state particles deform and bond has not been well characterized. It seems plausible, though it has not yet been demonstrated, that plastic deformation may disrupt thin surface films, such as oxides, and provide intimate conformal contact under high local pressure, thus per-

Environmental and economical analyses of transcritical CO2 heat pump combined with direct dedicated mechanical subcooling (DMS) for space heating in China

Abstract: An environmental and economical assessment model is developed, in order to evaluate the performances of transcritical CO2 heat pump system with dedicated mechanical subcooling (CO2 HPDMS). Introducing DMS to traditional CO2 HP system is an efficient method to reduce the primary energy consumption, which can be further decreased by using small temperature difference fan-coil unit (STD-FCU) as heating terminal. Using CO2 heat pump system for space heating is an environmentally-friendly heating method. The corresponding pollution emissions are only inferior to those of the wall hanging gas heater. The initial capital cost and operating cost of CO2 HPDMS system are both lower than those of CO2 HPBASE system, and the CO2 compressor cost accounts for about 80% of the overall initial capital cost. In contrast to other traditional heating methods, the payback periods of CO2 HPDMS system are not more than 9 years in most cases. If the CO2 compressor and electricity price are reduced by 20% and 28.79% respectively, the life cycle cost of CO2 HPDMS will be competitive to that of coal-fired boiler. In China, it is a promising way to adopt CO2 HPDMS for space heating in the near future with the assistant of electricity price subsidy and compressor price reduction.