4. Match the terms and their definitions.

1. heat	A. a device for transferring the heat of one substance to another
2. convector	B. apparatus for radiating heat from steam or hot water supplied through pipes
3. boiler	C. enclosed fireplace for heating building with hot water or steam
4. radiator	D. apparatus (for heating a room) by which air is warmed as it passes over hot surfaces
5. heat exchanger	E. a form of energy arising from the random motion of the molecules of bodies, which may be transferred by conduction, convection, or radiation
6. furnace	F. metal container in which water is heated

Reading Practice

5. Read the text thoroughly and translate it in written form. Text a. Central Heating Systems. Principles and Design.

In order to provide a comfortable temperature environment for occupants in an enclosure, a central heating system must convert a source of energy into heat energy at one location and transport this energy to other locations in the structure for the purpose of off–setting the heat losses of the building.

Fig. 1. Schematic diagram showing the components of a central heating system.

T he principal types of central heating systems are identified by the type of transport medium used to convey the heat energy.Water, steam, and air constitute the most common trans­port mediums. Thus, hot water, steam, and warm air are the three general types of heating systems. While the exact method of providing a comfortable environment varies with the type of system, each may be considered to consist of the components illustrated schematically in Fig.1.

A source of energy (usually coal, oil, gas, or electricity ) is applied to an energy converter (A), which changes the form of energy to heat energy. This heat energy is then transferred through a heat exchanger (B) to the transport medium (C), which conveys the heat energy to the heat–emitting device(D), where the heat is released to the space to be heated. After the heat release has occurred, the transport medium is returned to the heat exchanger to be reheated.

In Table 1, the basic components for the three general types of heating systems are identified in terms of the usual trade terminology.

Function	Hydronic systems		Warm air systems
(A) Energy converter	Steam Combustion process – most common. Electric apparatus – possible	Hot water Combustion process – most common. Electric apparatus – possible	Combustion process – most common. Electric apparatus – frequently.
(B) Heat exchanger	Boiler	Boiler	Furnace or coil
(C) Transport medium	Steam through copper or black iron pipes	Water through copper or black iron pipes	Air through ducts of sheet metal or other thin–walled conduits
(D) Heat–emitting device	Radiators, convectors, or baseboard units	Radiators, convectors, baseboard units or embeded coils of pipe	Registers, grilles,or diffusers

Table 1 – Basic components of central heating systems

This is an elementary tabulation, since many designs for large installation include many special, complex components that cut across the three general types. For example, in large industrial installations, the transport medium in the ducts may be air, but the heat exchanger may contain hot water, which is provided by a boiler.

Modern heating systems, whether installed in the largest skyscraper or the smallest house, normally provide draft–free and even–temperature heat, quiet and clean operation, and automatic performance at a reasonable cost with a minimum of service. These systems are often combined with summer air cooling and other air conditioning functions.

Certain design principles are common to all types of heating systems and buildings. First, the heat loss of the building and its rooms must be determined for a design day. This is the typical winter day at the building location for which the heating system must produce comfortable room temperatures under normal operation. For commercial and public buildings or houses designed by architects, the heat loss is calculated from data taken from the architectural plans.

Second, the type of heating system must be selected to match the calculated heat loss. For larger buildings, either a hydronic (hot–water or steam) system or a combination hydronic and air–handling system probably would be selected. For homes a forced warm–air or a forced hot–water system probably would be chosen, but in some cases the choice might be some form of electric heating system.

Next, the correct location of air registers, convectors, heating panels, and other equipment must be determined to ensure even temperature distribution and air movement throughout the rooms of the building. Then the proper size of any connecting ducts or pipes is calculated, and the duct or pipe runs are properly located on the building plans. The automatic control system is then worked out, and auxiliary components, such as filtering and humidifying equipment, are determined.

Complete heating plans and specifications usually are prepared for all buildings erected from architectural plans.

Notes:

enclosure – огороженное пространство

input – подача; подвод

space – пространство

reheat – повторно нагревать; подогревать

Comprehension Check