ARCH 3003 - Environmental Controls 1: Thermal Control: Designing for Heating and Cooling

Comprehensive vocabulary flashcards covering basic thermal processes, heat transfer principles, heating/cooling load calculations, and HVAC system types from the ARCH 3003 lecture.

Temperature

A measure of stored heat energy within a material or space.

Heat

Transferrable energy that always flows from hot to cool objects, which may cause a change in temperature (sensible heat) or a change of state (latent heat).

Specific Heat

The number of Btu's required to change the heat of a material by $1^\bullet\text{F}$, measured relative to the heat storage capacity of water.

British Thermal Unit (Btu)

The unit of heat measurement defined as the amount of heat energy required to raise one pound of water by $1^\bullet\text{F}$.

Radiation

The transfer of heat between two objects that are not in direct contact and not shielded from each other, propagating via electromagnetic wavelengths based on object temperature.

Emissivity

A surface property closely related to absorptivity that determines how effectively a material emits radiant energy; dark surfaces have high emissivity while white surfaces have low emissivity.

Transmissivity

A measure of how easily a material allows radiant energy to pass through it.

Greenhouse Effect

A phenomenon where glass allows shortwave visible light to pass into a space but blocks longwave infrared thermal radiation from escaping, trapping heat inside.

Conduction

The heat transfer process occurring in any direction between objects or materials in direct physical contact.

Latent Heat

Heat energy absorbed or released during a phase change of a material (such as liquid water converting to steam or atmospheric humidity) without changing its temperature.

Sensible Heat

Heat transfer that causes a direct, measurable change in temperature.

Convection

A heat exchange process occurring exclusively within a fluid medium (air or liquid), where heat transfers horizontally or upward, but never downward.

Stagnation

A convection phenomenon in which hot air rises to the top of a space and remains stationary.

Stack Effect

A natural convective process where warm, less dense air rises, expands, increases upper-level pressure to escape through cracks, and creates negative pressure below that draws cooler air inside.

Thermal Resistance ($R\text{-Value}$)

The measure of a material's opposition to heat flow, calculated as material thickness divided by its conductivity ($R = \frac{x}{k}$).

Overall Coefficient of Heat Transfer ($U\text{-Value}$)

The rate of heat transfer through a structural assembly, calculated as the reciprocal of the total thermal resistance ($U = \frac{1}{\sum R}$).

Degree Day

A metric representing how cold a given place has been over a specific period, evaluated relative to a baseline temperature ($65^\circ\text{F} - 1^\circ$).

Infiltration Load ($q_i$)

The thermal energy required to heat or cool replacement outdoor air that leaks into a building envelope through cracks, gaps, and penetrations.

Temperature Gradient

The distribution of temperature loss across individual material layers of a wall, expressed as $\Delta T_{\text{layer}} = \left(\frac{R_{\text{layer}}}{R_{\text{total}}}\right) \times \Delta T_{\text{total}}$.

Cooling Load Temperature Differential (CLTD)

A manual methodology introduced in the 1979 ASHRAE handbook that estimates building cooling loads by factoring wall mass, color, orientation, and solar cooling factors.

Plant

The central primary HVAC equipment—such as boilers, chillers, or rooftop units—that generates warm or cool air or water.

System

The distribution mechanism consisting of ducts, pipes, and terminal devices that delivers conditioned air or water throughout building zones.

Furnace

A central heating plant that heats air directly by burning fuel inside a combustion chamber and moving warm air by fan or convection.

Boiler

A specialized water-heating plant that uses natural gas or oil combustion to produce hot water or steam for hydronic distribution systems.

Heat Pump

A reversible HVAC plant that uses a small amount of energy to extract heat from the ground or air and transfer it into or out of a building.

Refrigeration Cycle

A closed-loop thermodynamic process that circulates refrigerant through an evaporator coil to absorb heat at low pressure and a condenser coil to release heat at high pressure.

Radiant Floor Heat

A hydronic heating system that circulates boiler-heated water through subfloor tubing to warm the floor surface and space occupants.

Ductless Mini-Split

An HVAC system that distributes heating or cooling energy through small refrigerant lines to individual indoor room fan/evaporator units without using ductwork.

Single Duct Constant Volume System

An air distribution system that delivers conditioned air at a constant volumetric flow rate through a single duct until the space thermostat is satisfied.

Double (Dual) Duct System

An HVAC air distribution system featuring separate hot and cold air supply ducts that blend in room terminal mixing boxes to serve adjacent zones.

Multizone System

An air distribution system that utilizes a central mixing box in the mechanical room to send pre-mixed conditioned air to specific zones via dedicated supply ducts.

Fan Coil System

An HVAC system that supplies clean ventilation air through a single duct and utilizes local room units equipped with fan coils connected to hot and cold water piping.

Variable Air Volume (VAV) System

A single duct air system that controls space temperature across different zones by varying the volumetric flow rate of supply air.

Unitary System

A ductless HVAC arrangement featuring self-contained wall or rooftop units that draw outdoor air directly into individual rooms or zones.

Single Pipe Hydronic System

A hydronic piping layout where a single continuous pipe functions as both supply and return, running sequentially through heating elements.

Two Pipe Hydronic System

A parallel hydronic piping arrangement using separate supply and return lines to prevent cooled return water from mixing back into the main supply line.

Three Pipe Hydronic System

A hydronic distribution layout with separate hot and cold supply pipes connected to terminal coils but returning water through a single shared return line.

Four Pipe Hydronic System

A hydronic distribution system providing complete isolation between heating and cooling circuits using independent supply and return lines for both.

Thermostat

A control device that senses room temperature and regulates HVAC operation to maintain desired setpoints.

Diffusers

Terminal air distribution components designed to control and direct the direction and spread of supply air into a space.

Dampers

Adjustable plates or valves located inside ductwork used to regulate or restrict airflow.

Vibration Isolator

Spring or elastomeric mounting components installed under mechanical equipment to absorb structural vibrations.