Propylene glycol is used as a filler for heating circuits and radiators for heating. In a closed system, the energy carrier should not contain impurities, chemicals, alkalis and salts that promote corrosion. The use of a ready-made coolant increases the operational characteristics of the boiler, reduces the destruction of the inner surface of pipes and batteries.
Features of the water heating system
The structure includes a heating boiler, piping network, batteries, circulation pump, collectors, external temperature meters, thermostats. Water passes through the heat exchanger of the unit, heats up and flows through pipes to the radiators of the heated space. The energy carrier gives off heat through the batteries and returns to the source. The coolant moves in a natural way or with the help of a pump.
Heating in the house is:
- gravitational (natural);
- forced.
The work is controlled by sensors and thermal heads in automatic mode or coordinated manually. In the system, the temperature is regulated separately on all devices, which saves fuel. The line uses a propylene glycol-based coolant, which extends the service life of equipment and devices. No sediment is deposited in the pipes, therefore 80–90% of the heat is given off.
The lack of water is that it freezes in unheated buildings, bursting collectors and radiators. Adding salt does not solve the problem, since it leads to increased corrosion, the inclusion of antifreeze in the coolant increases the cost of heating.
Description of propylene glycol
The substance is actively used in heating circuits due to its non-toxicity and safety. It is a viscous colorless liquid with a characteristic odor, which is used in many industries.
Liquid properties:
- the solution can withstand temperatures from -40 to + 100 ° С without changing the state, for a pure substance the operating parameters are in the range of -60 - + 185 ° С;
- the substance contains up to 5% carboxylates, which protect the inside of the pipe from destruction;
- anti-corrosion, anti-scale and stabilizing additives are added to the glycol for heating.
The density of propylene glycol is lower than that of glycerin and ethylene glycol, but higher than that of ethanol. The viscosity of the substance is higher than that of alcohols and ethylene glycol, especially in cold conditions. A substance is produced from propylene oxide by hydration at +160 - + 200 ° C under a pressure of 1.6 MPa.
The reaction takes place in a vacuum, in the process it is released:
- propylene glycol - 85%;
- dipropylene glycol - 13%;
- tripropylene glycol - 2%.
The finished product is stored for a year without changing its qualities. After that, the substance is divided into additives and a base, which reduces the heat capacity of propylene glycol.
Specifications
The product is used as a basis for an energy carrier with which the system is not afraid of freezing. Inexpensive pipes can be used as the substance contains anti-corrosive components.
Freezing point depending on the concentration of propylene glycol:
- contains 54% of the substance - the energy carrier freezes at -40 ° С;
- 48% - -30 ° C;
- 39% - -20 ° C;
- 25% - -15 ° C;
- 15% - -5 ° C.
In the system with the substance, storage boilers are used; in heating with ethylene glycol, the use of such units according to the instructions is not allowed. The disadvantage of propylene glycol, like ethylene glycol, is considered to be increased fluidity, due to which the liquid penetrates into cracks inaccessible to water. Seams and fittings are welded carefully to prevent leaks.
The propylene glycol heat transfer medium is used only in a system with the appropriate technical characteristics, so changing the water does not always lead to good results. Manufacturers of radiators indicate in the passport the compliance of products with one or another type of energy carrier.
The product is miscible with water, alcohols, ethylene, acids, organics of the carbonyl group, amines and nitrogen-containing solutions.
Advantages and disadvantages
In water at temperatures above + 75 ° С carbonates decompose, scale is deposited. Propylene glycol inhibits the corrosion process, ideally if added to distilled liquid.
The advantages of using an energy carrier with additives:
- protects the heating circuit and devices from rupture in frost, freezing occurs slowly with gradual crystallization;
- the frozen substance in the pipes receives a working consistency when the heating unit is started;
- the second in environmental safety coolant after water, prolonged inhalation of vapors, swallowing, contact with the skin is not dangerous;
- does not damage materials in contact with floor and wall finishes;
- promotes rapid heating and slow cooling of the system;
- reduces hydraulic resistance and improves the functioning of the pump in the return line;
- reduces electricity consumption when pumping energy, due to its low density.
The disadvantages include high cost compared to other types. But the high cost is justified by minimizing repairs, reducing the amount of fuel and labor costs. The substance is not used in heating mains where there are galvanized elements.
Differences between propylene glycol and ethylene glycol
Ethylene glycol is an organic acid-containing solution, a representative of polyhydric alcohols. It is a colorless, odorless, transparent liquid of oily density. Ingestion causes toxic poisoning.
Differences from propylene glycol:
- when freezing, the volume of water with propylene glycol increases by only 0.1%, and the coolant with ethylene glycol increases by 1.5%;
- the energy carrier with propylene glycol withstands the evaporation of water from the solution and does not freeze down to -60 ° С, ethylene glycol crystallizes at -13 ° С, glycerin - + 17 ° С;
- the toxicity of propylene glycol LD50 is from 20 to 30 thousand mg / kg, a similar indicator of ethylene glycol - LD52 - 4700 mg / kg.
The toxic substance is rapidly absorbed into the body, causing pulmonary edema and heart failure. The substance is not used in open systems, as it penetrates the skin and through inhalation. Waste energy carrier based on ethylene glycol is not poured into the ground or sewer, but is given for recycling.
Criterias of choice
When determining the type, the operating temperature at which the energy carrier exists for a certain time without decomposition is taken into account. The properties of the fluids are described and allow you to choose an additive according to the characteristics of the heating system.
Indicators are taken into account:
- heat capacity shows the volume of the energy carrier, which will provide the required heat per unit of time;
- corrosive activity indicates the need to select pipes and batteries and the impossibility of using with some materials;
- viscosity determines the speed of fluid movement, affects leaks, heat transfer coefficient, the indicator changes when heated or cooled;
- the lubrication rate limits the use of certain materials and designs of various mechanisms in contact with the product.
Safety for humans, the ability to cause burns, toxic poisoning are important. The flammability limit, the possibility of damage to objects when spilled from the system are taken into account.
Scope and features of the use of propylene glycol
The substance is used in the production of unsaturated polyester resins for the construction and automotive industries, in the production of alkyd mastics and polyurethanes. The product is used in the manufacture of creams, pastes, detergents in the cosmetic and pharmaceutical industries. The food industry uses propylene glycol to dissolve additives, and uses bactericidal and preservative properties.
The substance is used in the production of antifreeze, brake, anti-icing fluids, serves as a plasticizer in the production of polyvinyl films and cellophane. Propylene glycol is added to visual smoke devices for stage performances.
Due to the loss of fluid in the circuit, it is often necessary to mix ethylene glycol and propylene glycol in the heating system. A compatibility test must be carried out before pouring. These substances are combined, but manufacturers use different additives, which, when combined, can form a precipitate. The ideal solution is to completely drain the heating medium before refilling.
The propylene glycol-based energy carrier can be used in heating mains that partially run outside the house or in the attic. The coolant is poured into the circuit under pressure or manually, but the system is preliminarily subjected to hydraulic tests. During operation, samples of the energy carrier are taken and the suitability is checked in the laboratory.
