BOMA-HVAC Verified Answers

BOMA-HVAC Verified Answers A metering device ️A component in an AC system That drastically decreases the temperature and pressure of the refrigerant moving from the condenser before it enters the evaporator. It is engineered to govern (regulate) the flow of refrigerant to help regulate pressure. Ammonia, gas, and helium ️Require one BTU to raise the temperature of 1 lb of water by 1°F. Calculation for volume of air ️Change inches to feet and multiply, then multiply by the airflow(CFM) Dew Point ️-At this temperature, moisture starts condensing from the air. -used to define the level that air can no longer hold extra moisture, it has reached 100% capacity. Dry Bulb ️The temperature reading found on a typical thermometer. Effective ️The temperature at which motionless saturated air would induce The same sensation of comfort as that induced by the actual conditions of temperature, humidity, and air movement. Energy ️The capacity or power to do work, such as the capacity to move an object in a given direction by the application of force. Enthalpy ( heat content of a substance) ️-The measurement of heat energy. - measured by BTU. Fan Law ️CFM= CFM1 X (RPM1 divided by RPM2) Force ️The mass that is multiplied by its acceleration. F= M X A How many BTU's are required to raise the temperature of 1 lb of water by 1°F? ️One BTU Kinetic Energy ️The energy exist due to the motion of an object. laminar flow ️- A streamline or viscous flow. - layers of water flowing over one another at different speeds with virtually no mixing between layers. - Fluid particles move in definite and observable paths or stream lines. - The flow is characteristic of viscous (thick) fluid or is one in which viscosity of the fluid plays a significant part. Latent heat of fusion ️Transformation of a liquid to a solid or a solid to a liquid. Latent heat of sublimation ️Transformation of a solid to a gas or a gas to a solid without it going through a liquid state. Latent heat of vaporization ️Transformation of a liquid to a gas or a gas to a liquid. Metabolic rate ️Everybody produces heat differently Moisture content (Humidity Ratio) ️The total weight of water vapor per pound of dry air Newton's law of cooling ️The rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings. Non-condensables ️Gases that have gotten into the system and doesn't mix with the refrigerant but adds the effect of adding its pressure to the refrigerant in the system which can produce high heat pressures and other non-desirable effects. Potential energy ️The energy stored in an object due to its position and height. It is measured by the amount of work done. Power ️The rate at which work is done upon an object. ( Power= time/work) (force X distance)/time Pressure at sea level ️14.69 to 14.7 PSI Properties of good refrigerant ️- Low boiling point - High heat content - High critical temperature - High latent heat of vaporization - Low specific heat of liquid - Low specific volume of vapor - Non-corrosive to metal - Non- flammable - Non-explosive - Non-toxic - Low cost - Easy to liquify at moderate pressure and temperature - Easy to locating leaks by odor or suitable leak indicator - Mixes we'll with oil Psychrometry ️- Looking at the interaction (relationship) of the moisture ( humidity) and the