What does TR mean in air conditioning

What does TR mean in air conditioning

Originally 1 TR was defined as the rate of heat transfer required to make 1 short ton (2000 lbs) of ice per day from water at 0^oC. American Society of Heating, Refrigerating and Airconditioning Engineers (ASHRAE) defines 1 TR as equivalent to a refrigeration capacity of 3516.85 W or 3023.95 kcal/h.

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 Superheat and Subcooling

Superheat and subcooling are critical to the refrigeration cycle, but can be tough concepts to visualize.

Let’s start with superheat:

Boiling is when a liquid gains heat and transforms into a vapor.

Superheat occurs when that vapor is heated above its boiling point.

Let’s say that refrigerant boils at 40 degrees at a low pressure in the evaporator. The vaporized refrigerant is continuously heated, elevating its temperature to become a 50-degree vapor. This increase in temperatureabovethe boiling point is known as superheat. The formula to calculate superheat uses the current temperature and boiling point.

In this example, the superheat is 10-degrees.

Superheat is critical in HVAC because it ensures the liquid refrigerant is boiled off before it leaves the evaporator and heads to the compressor. Even small amounts of liquid can cause detrimental damage to the compressor in an HVAC system.

While evaporation and superheat occur in the evaporator, condensation and subcooling occur in the condenser.

Condensation is when a vapor loses heat and turns into a liquid, butsubcooling is when that liquid is cooled below the temperature at which it turns into a liquid.

Let’s use the same refrigerant with a high pressure boiling point of 120 degrees for the following example:

The refrigerant is a 140 degree vapor heading into the condenser. Once the condenser cools the refrigerant to 120 degrees, it will begin to turn back into a liquid. But the cooling does not stop there! Subcooling is also calculated using the boiling point (sometimes referred to as the condensing point) and current temperature.

So, if the condenser brings the refrigerant temperature down to 105 degrees, it has been subcooled by 15 degrees. In the refrigeration cycle, subcooling is an important process that ensures liquidrefrigerant enters the expansion device.

Key takeaways: superheat occurs in the evaporator to protect the compressor, and subcooling occurs in the condenser to protect the expansion device

HVAC Basic

HVAC Basics

Facility maintenance managers, HVAC contractors; HOA board members; estate and high-rise building managers; building and facility engineers; and commercial property managers all have one important responsibility to think about - running an HVAC.

Heating, cooling and air conditioning is vital to any part of real estate, whether for residential, commercial or industrial purposes.

Here's a list of HVAC system fundamentals:

What is HVAC?

Heating, Ventilation and Air Conditioning systems are tasked with circulating fresh air within living spaces, while maintaining the optimal temperature to keep the occupants comfortable. Maintaining an efficient, working HVAC system is paramount to keeping management smooth and providing thermal comfort.

Parts of an HVAC System

Property managers should have an idea of how an HVAC system operates and what to do when complications occur. Here are the most important things to remember about each part:

Compressor

The heart of an HVAC system, compressors pump the refrigerant through respective components in a looping pattern. The refrigerant enters the compressor as low-pressure vapor and exits as high-pressure vapor.

Condenser Coil

This HVAC system component is responsible for rejecting the heat load absorbed by the evaporator coil. If the condenser oil is neglected, improper cooling will occur causing a high head pressure.

Evaporator Coil

This component absorbs the heat load to the condenser coil for eventual rejection. If the evaporator coil is impacted or dirty, then the HVAC will have improper cooling and low suction pressure.

Condenser Fan Motor

Condenser fan motors help in rejecting the heat load and maintaining optimal head pressure for optimal compressor operation.

Evaporator Blower Motor

Evaporator blower motor is designed to force or push manipulated air through the duct stream.

Thermostatic Expansion Valve

The TXV is a device that regulates the amount of liquid refrigerant flowing through the evaporator. It is designed to maximize evaporator efficiency while diverting the flow of excess refrigerant back into the compressor (called floodback).

Cooling Tower

A component of an HVAC system which rejects the heat load absorbed by either the heat pump or evaporator coil carried by water. The water in it transports the heat load which was absorbed by the evaporator coil, dissipating it in the cooling tower. The water that passes via the heat exchanger normalizes head pressure.

Chiller

This is a machine that provides chilled water, which is used in conjunction with the HVAC system's cooling.

Pumps

These components are primarily designed to move water at the chill water and condenser water supply sections. Pumps move water chilled to 44 degrees to fancoils, and once the water reaches the fancoil, temperature rises to roughly around 47-52 degrees. Pumps that move the condenser water supply are rejected at cooling temperatures ranging from 90 to 100 degrees. Factors such as demand load, ambience, the cooling tower fill's condition, and strainers can vary the temperature during circulation.

Duct System

This can either be rectangular or spiral, flanged or drive. The main trunk line is where the main HVAC air flows, branching out to distribution points that carry the cooled or warmed air into small office suites and large conference rooms in commercial buildings.

Boiler

The boiler is pressure equipment which heats water. The choices when it comes to selecting boiler types are either low or high pressure systems, or hot water and steam.

Energy Management Monitoring Systems

Also known as BAS (Building Automation Systems), this HVAC component helps schedule, control and monitor commercial equipment such as cooling towers, pumps, package units, air compressors and handlers, boilers, temperature sensors, chillers and VAV boxes within the office and in office living spaces.