Central heating system

Glass-reinforced grades have widely replaced metals in pumps and other functional parts in washing equipment and central heating systems. In the manufacture of business machine and computer housings structural foam materials have found some use. Mouldings weighing as much as 50 kg have been reported. 

In buildings that are divided into zones with a central heating system, it is common to change the water temperature depending on the outdoor temperature. In this example a function called feed-forward or compensating is used. Figure 9.55 shows how the water temperature changes as a function of the outdoor temperature. 

In de-aerated conditions, for instance in most central heating systems, little if any attack on copper occurs . As far as drinking waters are concerned, copper is not classified as a toxic substance or hazardous to health. To avoid any difficulties due to unpalatability, the maximum continuous copper content should not exceed 10 p.p.m., with a limit of 3 p.p.m. in water after standing overnight in copper pipes. A review of the subject by Grunau makes reference to 394 published papers. 

The solubility of oxygen in water is influenced by several factors but, generally, most waters contain, at equilibrium, about 8mg/kg at 25°C, although supersaturation may increase this considerably. Some indication of the amount of dissolved oxygen relevant in different situations is shown, on the one hand, by the value of 0-1 mg/kg found in central heating systems and, on the other hand, by the value of 0 005 mg/kg specified by most users of large boilers as the upper limit at the economiser inlet (see Section 5.5). 

Process variables requiring control in a system include, but are not limited to, flow, level, temperature, and pressure. Some systems do not require all of their process variables to be controlled. Think of a central heating system. A basic heating system operates on temperature and disregards the other atmospheric parameters of the house. The thermostat monitors the temperature of the house. When the temperature drops to the value selected by the occupants of the house, the system activates to raise the temperature of the house. When the temperature reaches the desired value, the system turns off. 

Worked Example 3.11 The wood mentioned in our title question is a complicated mixture of organic chemicals so, for simplicity, we update the scene. Rather than prehistoric men sitting around a fire, we consider the calorific value of methane in a modem central-heating system. Calculate the value of A Hc for methane at 25 °C using molar enthalpies of formation AH. ... 

Air-to-air flue economizers are also available for about 1/5 the cost but these save much less energy and are usually not tied into the central heating system. They are best for heating spaces near the flue. 

The burners are used in room space heaters, water heaters, and central heating systems. Both natural air draft and forced air draft versions are available. 

The three principal fuels for domestic central heating systems are coal, fuel oil, and gas. The growth of fuel oil has been mostly at the expense of the hand-fired coal furnace. One of the main attractions of fuel oil was automatic heat, and the automatic coal stoker was for a time a lively competitor. Lately its popularity has very much declined. Within recent years the extension of natural gas lines has resulted in increased popularity for gas heating, and in 1950 the sales of gas burners actually surpassed the sales of oil burners, as shown by the following percentage figures on sales of automatic heating equipment gas burners, 56.3% oil burners, 42.6% and automatic stokers, 1.1%. 

Propagas is used in some central heating systems where natural gas is not available. It burns according to the following equation ... 

The gaseous alkanes are some of the most useful fuels. Methane, better known as natural gas, is used for cooking as well as for heating offices, schools and homes (Figure 14.5a). Propane and butane burn with very hot flames and they are sold as liquefied petroleum gas (LPG). In rural areas where there is no supply of natural gas, central heating systems can be run on propane gas (Figure 14.5b). Butane, sometimes mixed with propane, is used in portable blowlamps and in gas lighters. 

As typical representatives for slow heat release appliances a soapstone stove and a tiled stove were used for the tests. The third type of slow heat release appliance was equipped with an integrated heat exchanger to supply hot water for a central heating system. This appliance was chosen to check the feasibility of the new test method in view of the necessary recording of the heat split between heat released to the room and heat released to the central heating system. 

Fuel combustion generally occurs in kitchens, so the concentrations of pollutants in kitchens are higher than those in bedrooms (Table 5) [12]. With regard to different kinds of heating systems, separate ones (with small coal stoves) in individual residence units have higher indoor pollution than central heating systems in winter (Table 6) [13]. 

First, poor quality fuels and unventilated stoves will continue to be largely used in rural areas though enormous advances in the optimization of energy patterns and development of central heating systems in urban areas have achieved in the past few years. So, structural reform and rational use of fuels, improvement of stoves and, ventilation systems will play key roles in controlling indoor air pollution in rural areas. 

Gas oil or fuel oil used for firing the boilers of central heating systems. 

These sets of results are used as inputs to calculate energy efficiency, carbon, and NO emissions of the central heating system. 

For a heat pump used in the central heating system, the refrigerant has to assess by selfdeclaration. 

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