How many kW in gcal. Units of measurement of energy, power and their correct use

Everyone, at least indirectly, is familiar with such a concept as “calorie”. What is it and why is it needed? What exactly does it mean? Such questions arise, especially if you need to increase it to kilocalories, megacalories or gigacalories, or convert it to other values, such as Gcal to kW.

What is a calorie

The calorie is not included in the international system of measurements of metric values, but this concept is widely used to refer to the amount of energy released. It indicates how much energy must be spent on heating 1 g of water so that this volume increases the temperature by 1 ° C under standard conditions.

There are 3 generally accepted designations, each of which is used depending on the area:

The international value of a calorie, which is equal to 4.1868 J (Joule), and is denoted as "cal" in Russian Federation and cal, in the world;
In thermochemistry - a relative value approximately equal to 4.1840 J with the Russian designation cal th and the world one - cal th;
A 15-degree calorie indicator equal to approximately 4.1855 J, which is known in Russia as “cal 15”, and in the world - cal 15.

Initially, the calorie was used to find the amount of heat released during the generation of energy from the fuel. Subsequently, this value began to be used to calculate the amount of energy expended by an athlete when performing any physical activity, since the same physical laws apply in these actions.

Since fuel is needed to release heat, then, by analogy with heat power engineering in a simple life, the body also needs “refueling” to generate energy - food that people take regularly.

A person receives a certain number of calories, depending on which product he consumed.

The more calories in the form of food a person received, the more energy he gets for sports. However, people do not always consume the amount of calories needed to maintain life processes organism in the norm and performance of physical activity. As a result, some lose weight (with a calorie deficit), while others gain weight.

Calorie is the amount of energy received by a person as a result of the absorption of a particular product.

Based on this theory, many principles of diets and rules are built. healthy eating. The optimal amount of energy and macronutrients that a person needs per day can be calculated in accordance with the formulas of well-known nutritionists (Harris-Benedict, Mifflin-San Geor), using standard parameters:

Age;
Growth;
An example of daily activity;
Lifestyle.

These data can be used by changing them for yourself - for painless weight loss, it is enough to create a deficit of 15-20% of the daily calorie content, and for a healthy weight gain - a similar surplus.

What is a gigacalorie and how many calories does it contain

The concept of Gigacalorie is most often found in documents in the field of thermal power engineering. This value can be found in receipts, notices, payments for heating and hot water.

It means the same thing as a calorie, but in a larger volume, as evidenced by the prefix "Giga". Gcal determines that the original value was multiplied by 10 9 . talking plain language: 1 Gigacalorie - 1 billion calories.

Like the calorie, the gigacalorie does not belong to the metric system of physical quantities.

The table below shows a comparison of values as an example:

The need to use Gcal is due to the fact that when heating the volume of water needed for heating and household needs of the population, even 1 residential building releases a huge amount of energy. Writing numbers denoting it in documents in calorie format is too long and inconvenient.

Such a value as a gigacalorie can be found in payment documents for heating

One can imagine how much energy is spent during the heating season on an industrial scale: when heating 1 quarter, district, city, country.

Gcal and Gcal/h: what is the difference

If it is necessary to calculate the payment by the consumer for state heat power services (house heating, hot water), such a value as Gcal / h is used. It denotes a reference to time - how many Gigacalories are consumed during heating for a given period of time. Sometimes it is also replaced by Gcal / m 3 (how much energy is needed to transfer heat to a cubic meter of water).

Q=V*(T1 – T2)/1000, where

V is the volume of fluid consumption in cubic meters/tons;
T1 is the temperature of the incoming hot liquid, which is measured in degrees Celsius;
T2 is the temperature of the incoming cold liquid, by analogy with the previous indicator;
1000 is an auxiliary coefficient that simplifies calculations by eliminating numbers in the tenth digit (automatically converts kcal to Gcal).

This formula is often used to build the principle of operation of heat meters in private apartments, houses or enterprises. This measure is necessary with a sharp increase in the cost of this utility service, especially when the calculations are generalized based on the area / volume of the room that is heated.

If a closed-type system is installed in the room (hot liquid is poured into it once without additional water supply), the formula is modified:

Q= ((V1* (T1 – T2)) – (V2* (T2 – T)))/ 1000, where

Q is the amount of thermal energy;
V1 is the volume of consumed thermal substance (water / gas) in the pipeline through which it enters the system;
V2 is the volume of thermal substance in the pipeline through which it returns back;
T1 - temperature in degrees Celsius in the pipeline at the inlet;
T2 - temperature in degrees Aim in the pipeline at the outlet;
T - temperature cold water;
1000 is an auxiliary coefficient.

This formula is based on the difference between the values at the inlet and outlet of the coolant in the room.

Depending on the use of a particular energy source, as well as the type of thermal substance (water, gas), alternative calculation formulas are also used:

Q= ((V1* (T1 - T2)) + (V1 - V2)*(T2 - T))/1000
Q= ((V2* (T1 - T2)) + (V1 - V2)*(T1 - T))/1000

In addition, the formula changes if electrical devices are included in the system (eg underfloor heating).

How Gcal for hot water and heating is calculated

Heating is calculated using formulas similar to the formulas for finding Gcal/h.

An approximate formula for calculating payment for warm water in residential premises:

P i gv \u003d V i gv * T x gv + (V v kr * V i gv / ∑ V i gv * T v kr)

Used quantities:

P i gv - the desired value;
V i gv - volume of consumption hot water for a certain time period;
T x gv - the established tariff fee for hot water supply;
V v gv - the amount of energy expended by the company that is engaged in its heating and supply to residential / non-residential premises;
∑ V i gv - the amount of consumption warm water in all premises of the house in which the calculation is made;
T v gv - tariff fee for thermal energy.

This formula does not take into account the atmospheric pressure indicator, since it does not significantly affect the final desired value.

The formula is approximate and is not suitable for self-calculation without prior consultation. Before using it, you must contact the local utilities for clarification and adjustment - perhaps they use other parameters and formulas for the calculation.

Calculation of the amount of heating payment is very important, as often impressive amounts are not justified.

The result of the calculations depends not only on relative temperature values - it is directly affected by the tariffs set by the government for the consumption of hot water and space heating.

The computational process is greatly simplified if you install a heating meter on an apartment, entrance or residential building.

It should be borne in mind that even the most accurate counters can allow errors in the calculations. It can also be determined by the formula:

E = 100 *((V1 - V2)/(V1 + V2))

The following indicators are used in the presented formula:

E - error;
V1 is the volume of consumed hot water supply upon admission;
V2 - consumed hot water at the outlet;
100 is an auxiliary coefficient that converts the result into a percentage.

In accordance with the requirements, the average error of the calculation device is about 1%, and the maximum allowable is 2%.

Video: an example of calculating the heating fee

How to convert Gcal to kWh and Gcal/h to kW

On the various devices the spheres of thermal power engineering indicate various metric values. Yes, on heating boilers and heaters often indicate kilowatts and kilowatts per hour. Gcal is more common on counting devices (counters). The difference in values interferes with the correct calculation of the desired value by the formula.

To facilitate the calculation process, it is necessary to learn how to translate one value into another and vice versa. Since the values \u200b\u200bare constant, this is not difficult - 1 Gcal / h is equal to 1162.7907 kW.

If the value is presented in megawatts, it can be converted back to Gcal / h by multiplying by a constant value of 0.85984.

Below are auxiliary tables that allow you to quickly convert values from one to another:

The use of these tables will greatly simplify the process of calculating the cost of thermal energy. In addition, to simplify the steps, you can use one of the online converters offered on the Internet that convert physical quantities one into the other.

Self-calculation of consumed energy in Gigacalories will allow the owner of residential / non-residential premises to control the cost utilities, as well as the work of public services. With the help of simple calculations, it becomes possible to compare the results with similar ones in the received payment receipts and contact the relevant authorities in case of a difference in indicators.

All summer long, the red gossips in soft furs sang and danced, and now, when the cold comes, you will have to take pencils in your hands. After all, "heating, as it was not, and is not." And it is necessary to present at least some arguments of the heating network, having calculated the heat received from it, for which, after all, it was “Paid”.

When you need to dot all the "i"

But a quite reasonable question arises: "But how to calculate what is invisible and capable of escaping in an instant, literally through the window." You should not despair of this struggle with the air, it turns out that there are quite intelligible mathematical calculations of the calories received for heating.

Moreover, all these calculations are hidden in the official documents of state utility organizations. As usual in these institutions, there are several such documents, but the main one is the so-called "Rules for accounting for thermal energy and coolant". It is he who will help solve the question - how to calculate Gcal for heating.

Actually, the problem can be solved quite simply and no calculations are needed if you have a meter not just for water, but for hot water. The readings of such a meter are already "filled" with data on the received heat. Taking readings, you multiply it by the cost rate and get the result.

Basic Formula

The situation becomes more complicated if you do not have such a counter. Then you have to follow the following formula:

Q = V * (T1 - T2) / 1000

In the formula:

Q is the amount of thermal energy;
V is the volume of hot water consumption in cubic meters or tons;
T1 is the hot water temperature in degrees Celsius. It is more accurate to use the temperature in the formula, but reduced to the corresponding pressure, the so-called "enthalgy". But in the absence of a better - the corresponding sensor, we simply use the temperature, which is close to the enthalpy. Professional heat metering units are able to calculate exactly the enthalpy. Often this temperature is not available for measurement, therefore, they are guided by the constant "from the ZhEKA", which can be different, but usually is 60-65 degrees;
T2 is the cold water temperature in degrees Celsius. This temperature is taken from the cold water pipe of the heating system. Consumers, as a rule, do not have access to this pipeline, therefore it is customary to take constant recommended values depending on the heating season: in the season - 5 degrees; out of season - 15;
The “1000” factor allows you to get rid of the 10-digit numbers and get data in gigacalories (instead of just calories).

As follows from the formula, it is more convenient to use a closed heating system, into which the required volume of water is once poured and in the future it does not flow. But in this case you are not allowed to use hot water from the system.

The use of a closed system makes it necessary to slightly improve the above formula, which already takes the form:

Q = ((V1 * (T1 - T)) - (V2 * (T2 - T))) / 1000

V1 is the flow rate of the coolant in the supply pipeline, regardless of whether water or steam serves as the coolant;
V2 - coolant flow in the return pipeline;
T1 is the temperature of the heat carrier at the inlet, in the supply pipeline;
T2 is the temperature of the coolant at the outlet, in the return pipeline;
T is the temperature of cold water.

Thus, the formula consists of the difference of two factors - the first gives the value of the incoming heat in calories, the second - the value of the output heat.

Useful advice! As you can see, there is not much mathematics, but the calculations still have to be done. Of course, you can immediately rush to your calculator on your mobile phone. But he advises you to create simple formulas in one of the most famous computer office programs - the so-called spreadsheet Microsoft Excel included in the Microsoft Office suite. In Excel, you can not only quickly calculate everything, but also “play” with the source data, simulate various situations. Moreover, Excel will help you with the construction of graphs for the receipt - heat consumption, and this is an "unkilled" map in a future possible conversation with government bodies.

Alternatives

How exist various ways providing housing with heat by choosing a coolant - water or steam, so there are alternative methods for calculating the heat received. Here are two more formulas:

Q = ((V1 * (T1 - T2)) + (V1 - V2) * (T2 - T)) / 1000

Q = ((V2 * (T1 - T2)) + (V1 - V2) * (T1 - T)) / 1000

Thus, the calculations can be done with your own hands, but it is important to coordinate your actions with the calculations of the organizations supplying heat. Their calculation instructions may be fundamentally different from yours.

Useful advice! Often reference books provide information not in the national system of units of measure, to which calories belong, but in international system"Si". Therefore, we advise you to remember the coefficient for converting kilocalories to kilowatts. It is equal to 850. In other words, 1 kilowatt is equal to 850 kilocalories. From here it is already easy to make the transfer of gigacalories, given that 1 gigacalories is a million calories.

All counters, and not only the simplest brownies, unfortunately suffer from some measurement error. This is a normal situation, unless, of course, the error does not exceed all conceivable limits. To calculate the error (relative, in percent), a special formula is also used:

R \u003d (V1 - V2) / (V1 + V2) * 100,

V1 and V2 are the previously considered coolant flow rates, and
100 is the conversion factor to percent.

The percentage of error in the calculation of heat is considered acceptable - no more than 2 percent, given that the error measuring instruments is no more than 1 percent. You can, of course, get by with the old proven method, here you don’t need to do any calculations.

Representation of received data

The price of all calculations is your confidence in the adequacy of your own financial costs for the heat received from the state. Although, in the end, you still will not understand what Gcal is in heating. Hand on heart, let's say that in many ways this is the value of our sense of self and attitude to life. Some base "in numbers", of course, you need to have in your head. And it is expressed in what is considered a good norm, when your formulas give 3 gcal per month for an apartment of 200 square meters. So if 7 months lasts heating season- 21 cal.

But all these quantities are rather difficult to imagine “in the shower”, when warmth is really needed. All these formulas and even the results they give you correctly will not warm you up. They will not explain to you why even at 4 Gcal per month, you are still warm. And the neighbor has only 2 Gcal, but he does not boast and constantly keeps the window open.

There can be only one answer here - his atmosphere is also warmed by the warmth of those around him, and you don’t have anyone to snuggle up to, although “the room is full of people.” He gets up in the morning at 6 and runs in any weather to exercise, and you lie until the last under the covers. Warm yourself from the inside, hang a photo of the family on the wall - all in summer in swimsuits on the beach in Foros, watch more often the video of the last ascent to Ai-Petri - everyone is naked, it's hot, then outside you won't even feel a lack of a couple of hundred calories.

COUNTING THERMAL ENERGY!

When you start to understand the issue of calculating thermal energy, it seems so complicated, you assume that only an academician can understand these calculations, and then with a specialization in housing and communal services (probably, this does not happen). But when you get used to the terms and get used to the essence of this issue, everything clears up and becomes less scary.

There is an opinion that in the post-Soviet space we, as always, differ from the rest of the planet and instead of counting thermal energy in joules (J), we consider it in long-standing non-systemic units of measurement calories, or rather, in units of measurement of thermal energy derived from calories - gigacalories ( Gcal). It's essentially the same thing, only with an extra nine zeros (109 calories).

Due to the fact that in various fields of activity different temperatures are taken as the reference temperature of water, there are several different definitions of calories in joules (J).
1 calm = 4.1868 J (1 J ≈ 0.2388459 kcal) International calorie, 1956.
1 cal = 4.184 J (1 J = 0.23901 cal) Thermochemical calorie.
1 cal15 = 4.18580 J (1 J = 0.23890 cal15) Calorie at 15°C.

The unit of measurement Joule (J), is a unit of energy in the CI system.
It is defined as the work of a force of one Newton at a distance of 1 meter, it follows that 1 J = 1 N * m = 1 kg * m ** 2 / sec ** 2. In turn, this is connected with the definition of the unit of mass in kilograms (kg), length in meters (m) and time in seconds (sec) in the CI system.
One J = 0.239 calories, one GJ = 0.239 Gcal, and one gigacalorie = 4.186 GJ.

Today, as is known to a greater extent, the beautiful half of humanity, it is customary to measure the energy value (calorie content) of food products - Kcal in calories. The whole world has long forgotten about the use of Gcal for evaluation in thermal power engineering, heating systems, utilities, and we persistently continue to count in this way.

But be that as it may, another derived unit of measurement Gcal / hour (gigacalorie per hour) appears from here. It then characterizes the amount of thermal energy used or produced by one or another equipment or coolant in one hour. Gcal / hour as a value is equivalent to thermal power, but we do not need this yet.

For a better understanding of the issue, let's take a look at some more units of measurement and do simple arithmetic calculations.

Once again, so, to consolidate understanding. One Calorie is equal to 1 calorie, one Kilocalorie is equal to 1000 calories, one Megacalorie is equal to 1,000,000 calories, one Gigacalorie is equal to 1,000,000,000 (1×109 calories)

One calorie releases the amount of heat that is needed to heat one gram of water by one degree Celsius at a pressure of one atmosphere (pressure will also be omitted for now, although this is the constant value of all formulas and its standard atmospheric pressure value is 101.325 kPa).

Now we can assume that Gigacalorie for one square meter total area premises, is the amount of heat energy consumption for space heating. And as confirmation of what has been said, this unit of measurement was provided for in the "Rules for the provision of public services for use in calculations."

In other words, one gigacalorie (Gcal) heats one thousand cubic meters of water per degree Celsius, or about 16.7 cubic meters of water per 60 degrees Celsius (1000/60=16.666667).

This information can be useful when evaluating the performance of hot water meters (HWP).

Heat meters keep their records in the unit of measurement Gcal or, rarely, in megajoules. It is known that power generating companies use Gcal in their calculations.

Each fuel during combustion has its own heat transfer indicators for a certain amount of this fuel, the so-called calorific value solid and liquid fuels are measured in Kcal/kg. If you are interested, look on the net, but as an example, I’ll say that the calculations use conventional fuel, the calorific value of which is equal to 7 Gcal per 1 ton of fuel, and for natural gas- 8.4 Gcal per 1 thousand cubic meters of gas.

If you have learned all these meanings, we can try to check the energy company or our neighbors heat terrorists without leaving the apartment!

How to check everyone without leaving the apartment?

According to the source of this information, if you can make all these calculations correctly, then based on your numbers, you will be able to check the energy company and file a claim with your operating organization or condominiums, demanding recalculation.

Let's try to do this using the data received on the forum at the site address: gro-za.pp.ua/forum/index.php?topic=4436.0

So, a few more numbers for "assimilation":

Kilowatt hour. It is used mainly in the calculations for electricity (in electricity meters). Derived from the unit of power, which is called the Watt (W) and is equal to the energy of 1 J used for 1 second.

For example, a 60 W electric light bulb consumes 60 Wg = 0.060 kWh of energy for 1 hour. Or in joules and kilocalories: 1 kWh = 3600 kJ = 860.4 kilocalories = 0.8604 megacalories; 1 gigacalorie = 1162.25 KWh = 1.16225 MWh (megawatt hours); 1 MWh = 0.8604 Gcal. The unit of power Watt is used in assessing the heat transfer of heating devices (heat radiators).

So how can this information be used to the benefit of the district heating consumer?

To do this, we need to assimilate some more data. Suggested below reference Information on heat transfer of two types of radiators.
If your type of radiator is not among these two, you are out of luck, so if you are "lucky" you will find detailed information about your type of radiator in the net or in some reference books.

SO, THE FIRST TYPE OF RADIATOR. The rated heat output of an aluminum radiator of the Calidor type by the Italian company Fondital (according to EN 442-2) is Q=194 W at Dt=(Trad-Tpov)=60 degrees Celsius, where Trad is the average water temperature in the radiator, Tpov is the air temperature in the room . Trad is equal to the difference in water temperature at the inlet and outlet of the radiator. With a single-pipe coolant supply, this difference is practically equal to the inlet temperature. For other values, Dt is the heat transfer value, which is taken with the correction factor K = ((Dt / 60)) ^ n, de ^ - exponentiation operation, n = 1.35.

Example: radiator temperature 45 degrees, air temperature 20 degrees. Then K \u003d ((45-20) / 60) ^ 1.35 \u003d 0.3067, and Q \u003d 194 x 0.3067 \u003d 59.5 W - three times less than the nominal value!

SECOND TYPE OF RADIATOR. The most common heating radiator is cast iron MS-140M4 500-0.9. The reference books indicate the power of thermal radiation for cast iron section MS-140 in the amount of 160-180 W at a coolant temperature of 90°C. But, this heat transfer is achievable only under ideal (laboratory) conditions, which in real life out of reach. Because the radiation power depends significantly on temperature, so the real heat transfer of the cast iron section at 60°C will be no more than 80 W, and at 45°C - about 40 W. The flow of heated water from the house system to cast iron battery happens randomly. In order for the average temperature of the entire radiator to be 60°C, it is necessary to ensure the supply of water with a temperature of at least 75°C, then water with a temperature of about 45°C will flow into the “return”. Calculate how powerful a heat exchanger should be in order to heat a ton of water to a temperature level of 75 ° C. It must be taken into account that ten degrees is spent in thick metal pipes that lead to the house. That's why elevator unit(heat exchanger) should give 85...90°C and work on the edge of the possible. Provide temperature cast iron radiator 90°C water (not steam) heating systems are impossible and unsafe - you can get burned at 70°C.
In addition, it should be noted that the curtains on the radiator lead to a decrease in heat transfer by 10–18%, the area of the cast-iron radiator, the coating oil paint gives a decrease in heat transfer by 13%, and coating with zinc white increases heat transfer by 2.5%.

Having data on the actual temperature of the heat carrier at the inlets of apartment heating radiators, data on the heat transfer (in Watts) of one section of the heat radiator at a nominal temperature, you calculate the actual heat transfer at the actual temperature of the heat carrier. Multiply the obtained data by the number of seconds of time during which the results of measurements / calculations took place. Get the amount of heat energy in Joules. Convert to gigacalories.

After that, you make a conclusion who owes whom and how much. If you are indebted, file a claim with the balance holder of the house with a request for recalculation.

EXAMPLE:
Let one section of the CH radiator actually deliver 30 watts. Let the area of the apartment be 84 sq.m. According to the above recommendation, you should have 1 section per 1 sq.m, that is, everything you need is 84 sections, or 6 radiators, 14 sections each. The power of one radiator is 30x14 = 420 W = 0.42 kW. During the day, one radiator will give 0.42x24 = 10.08 kWh of heat energy, and 6 radiators - respectively 10.08x6 = 60.48 kWh. For a month we will get 60.48x30 \u003d 1814.4 kWh. We translate into gigacalories: (1814.4 / 1000) = 1.8144 Mvtg. x 0.8604 = 1.56 Gcal. The heated season lasts 6 months, of which more or less full heating is needed for 5 months, because in the first half of April the weather is already warm. And the second half of October is also frost-free. Thus, with the marked parameters, you will get 1.56 x 5 \u003d 7.8 Gcal. instead of the standard 0.147 Gcal/sq.m x 84 sq.m = 12.348 Gcal. That is, you received only 100% x 7.8 / 12.348 = 63% of the standard volume of heat energy, and 37% are extra accrued funds for central heating.

I hope everyone understands everything, and if it is not clear, then it's not my fault!

Be that as it may, I think that we are already ready for the main section of our conversation.

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Often, one of the problems faced by consumers both in private buildings and in apartment buildings is that the consumption of thermal energy obtained in the process of heating a home is very large. In order to save yourself from the need to overpay for excess heat and to save money, you should determine exactly how the calculation of the amount of heat for heating should take place. The usual calculations will help to solve this, with the help of which it will become clear what volume the heat entering the radiators should have. This is what will be discussed next.

General principles for performing Gcal calculations

The calculation of kW for heating involves the performance of special calculations, the order of which is regulated by special regulations. The responsibility for them lies with the communal organizations that are able to help in the performance of this work and give an answer on how to calculate Gcal for heating and decipher Gcal.

Of course, such a problem will be completely eliminated if there is a hot water meter in the living room, since it is in this device that there are already pre-set readings that display the received heat. By multiplying these results by the established tariff, it is fashionable to obtain the final parameter of the consumed heat.

Order of calculations when calculating the consumed heat

In the absence of such a device as a hot water meter, the formula for calculating heat for heating should be as follows: Q \u003d V * (T1 - T2) / 1000. The variables in this case display values such as:

Q in this case is the total amount of heat energy;
V is an indicator of hot water consumption, which is measured either in tons or in cubic meters;
T1- temperature parameter hot water (measured in the usual degrees Celsius). In this case, it would be more appropriate to take into account the temperature that is typical for a certain working pressure. This indicator has a special name - enthalpy. But in the absence of the required sensor, one can take as a basis the temperature that will be as close as possible to the enthalpy. As a rule, its average value varies from 60 to 65 ° C;
T2 in this formula is the temperature indicator of cold water, which is also measured in degrees Celsius. Due to the fact that getting to the pipeline with cold water very problematic, such values are determined by constant values, which differ depending on weather conditions outside the home. For example, in winter time year, that is, at the very height of the heating season, this value is 5 ° C, and in summer, when the heating circuit is turned off - 15 ° C;
1000 is a common factor that can be used to get the result in gigacalories, which is more accurate, and not in regular calories. See also: "How to calculate heat for heating - methods, formulas".

The calculation of Gcal for heating in a closed system, which is more convenient for operation, should take place in a slightly different way. The formula for calculating space heating with closed system is as follows: Q = ((V1 * (T1 - T)) - (V2 * (T2 - T))) / 1000.

In this case:

Q is the same amount of thermal energy;
V1 is the parameter of the coolant flow in the supply pipe (both ordinary water and steam can act as a heat source);
V2 is the volume of water flow in the outlet pipeline;
T1 - temperature value in the heat carrier supply pipe;
T2 - outlet temperature indicator;
T is the temperature parameter of cold water.

We can say that the calculation of heat energy for heating in this case depends on two values: the first of them displays the heat entering the system, measured in calories, and the second is the thermal parameter when the coolant is removed through the return pipeline.

Other ways to calculate the amount of heat

It is possible to calculate the amount of heat entering the heating system in other ways.

The calculation formula for heating in this case may differ slightly from the above and have two options:

Q = ((V1 * (T1 - T2)) + (V1 - V2) * (T2 - T)) / 1000.
Q = ((V2 * (T1 - T2)) + (V1 - V2) * (T1 - T)) / 1000.

All values of the variables in these formulas are the same as before.

Based on this, it is safe to say that the calculation of kilowatts of heating can be done with your own on their own. However, do not forget about consulting with special organizations responsible for supplying heat to dwellings, since their principles and calculation system can be completely different and consist of a completely different set of measures.

Having decided to design a system of the so-called “warm floor” in a private house, you need to be prepared for the fact that the procedure for calculating the volume of heat will be much more difficult, since in this case it is necessary to take into account not only the features of the heating circuit, but also provide for the parameters electrical network from which the floor will be heated. At the same time, the organizations responsible for controlling such installation work, will be completely different.

Many hosts often face the problem of transferring the right amount kilocalories to kilowatts, which is due to the use by many auxiliary aids of measuring units in the international system called "Ci". Here you need to remember that the coefficient that converts kilocalories to kilowatts will be 850, that is, in simpler terms, 1 kW is 850 kcal. This calculation procedure is much simpler, since it will not be difficult to calculate the required amount of gigacalories - the prefix "giga" means "million", therefore, 1 gigacalorie - 1 million calories.

In order to avoid errors in calculations, it is important to remember that absolutely all modern ones have some error, and often within acceptable limits. The calculation of such an error can also be done independently using the following formula: R = (V1 - V2) / (V1 + V2) * 100, where R is the error, V1 and V2 are the parameters of water flow in the system already mentioned above, and 100 - coefficient responsible for converting the obtained value into a percentage.

In accordance with operating standards, the maximum allowable error can be 2%, but usually this figure in modern devices does not exceed 1%.

Total of all calculations

A correctly performed calculation of the consumption of thermal energy is a guarantee of the economical expenditure of financial resources spent on heating. As an example of an average value, it can be noted that when heating a residential building with an area of 200 m², in accordance with the above calculation formulas, the amount of heat will be approximately 3 Gcal per month. Thus, taking into account the fact that the standard heating season lasts six months, then for six months the volume of consumption will be 18 Gcal.

Of course, all measures for calculating heat are much more convenient and easier to carry out in private buildings than in apartment buildings with a centralized heating system, where simple equipment cannot be dispensed with. See also: "How is heating calculated in an apartment building - rules and calculation formulas".

Thus, we can say that all calculations to determine the heat energy consumption in a particular room can be done on their own (read also: ""). It is only important that the data be calculated as accurately as possible, that is, according to mathematical formulas specially designed for this, and all procedures should be agreed with the special authorities that control the conduct of such events. Help with calculations can also be provided professional craftsmen, regularly engaged in such work and having various video materials available that describe in detail the entire calculation process, as well as photos of samples heating systems and wiring diagrams.

Let's start with the concepts of "work" and "power". Work is a part of the internal energy expended by a person or machine over a certain time period. In the process of such work, a person or machine warms up, releasing heat. Therefore, both internal energy and the amount of heat released or absorbed, as well as work, are measured in the same units - joules (J), kilojoules (kJ) or megajoules (MJ).

The faster work is done or heat is released, the more internal energy. A measure of this intensity is the power, measured in watts(W), kilowatts (kW), megawatts (MW), and gigawatts (GW). Power is the work done per unit of time (whether it is the work of the engine, or the work electric current). Thermal power is the amount of heat transferred per unit time to the coolant (water, oil) from the combustion of fuel (gas, fuel oil) in the boiler.

The calorie was introduced as early as 1772 Swedish experimental physicist Johann Wilke as a unit of heat. Currently, a unit that is a multiple of calories - gigacalorie (Gcal), is actively used in such areas of life as utilities, heating systems and thermal power engineering. Its derivative is also used - gigacalorie per hour (Gcal / h), which characterizes the rate of heat release or heat absorption by one or another equipment. Now let's try to calculate what one calorie is equal to.

Even at school, in physics lessons, we were taught that in order to heat any substance, it needs to be imparted a certain amount of heat. There was even such a formula Q = c * m * ∆t, where Q means an unknown amount of heat, m is the mass of the heated substance, c is the specific heat of this substance, and ∆t is the temperature difference by which the substance is heated. So, a calorie is called an off-system unit of the amount of heat, defined as "the amount of heat spent on heating 1 gram of water by 1 degree Celsius at an atmospheric pressure of 101325 Pa".

Since heat is measured in joules, using the formula above, we find out what is 1 calorie (cal) in joules. To do this, take the value from the reference book on physics specific heat water under normal conditions (atmospheric pressure p=101325 Pa, temperature t=20°C): c=4183 J/(kg*°C). Then one calorie will be equal to:

1 cal \u003d 4183 [J / (kg * ° C)] * 0.001 kg * 1 ° C \u003d 4.183 J.

However, the calorie value depends on the heating temperature, so its value is not constant. For practical purposes, the so-called international calorie or simply calorie is used, which is equal to 4.1868 J.

Memo 1

1 cal=4.1868 J, 1 kcal=1000 cal, 1 Gcal=1 billion cal=4186800000 J=4186.8 MJ;
1 J = 0.2388 cal, 1 MJ = 1 million J = 238845.8966 cal = 238.8459 kcal;
1 Gcal/h=277777.7778 cal/s=277.7778 kcal/s=1163000 J/s=1.163 MJ/s.

gigacalories or kilowatts

Let's finally figure out what is the difference between these units of measurement. Suppose we have a heating device, for example, a kettle. Let's take 1 liter of cold tap water (temperature t1=15°C) and boil it (heat it up to temperature t2=100°C). Electric power kettle - P=1.5 kW. How much heat will the water absorb? To find out, we apply the familiar formula, taking into account that the mass of 1 liter of water is m=1 kg: Q=4183 [J/(kg*°C)]*1 kg*(100°С-15°С)= 355555 J = 84922.8528 cal≈85 kcal.

How long does it take for the kettle to boil? Let all the energy of the electric current go to heat the water. Then we will find the unknown time using the energy balance: "The energy consumed by the kettle is equal to the energy absorbed by water (without taking into account losses)". The energy consumed by the kettle during time τ is equal to P*τ. The energy absorbed by water is equal to Q. Then, based on the balance, we get P*τ=Q. From here, the heating time of the kettle will be: τ=Q/P=355555 J/1500 W≈237 s≈4 min. The amount of heat transferred by the kettle to water per unit of time is its heat output. In our case, it will be Q/τ=84922.8528 cal/237 s≈358 cal/s=0.0012888 Gcal/h.

In this way, kW and Gcal/h are power units, and Gcal and MJ are units of heat and energy. How can such calculations be applied in practice? If we receive a receipt for paying for heating, then we pay for the heat that the supply organization supplies to us through pipes. This heat is taken into account in gigacalories, i.e., in the amount of heat consumed by us during the billing period. Should this unit be converted to joules? Of course not, because we're just paying for a specific number of gigacalories.

However, it is often necessary to choose certain heating devices for a house or apartment, for example, an air conditioner, a radiator, a boiler or a gas boiler. In this connection, it is required to know in advance the thermal power required to heat the room. Knowing this power, you can choose the appropriate device. It can be specified both in kW and Gcal / h, as well as in units of BTU / h (British Thermal Unit - British Thermal Unit, h - hour). The following note will help you convert kW to Gcal/h, kW to BTU/h, Gcal to kWh and BTU to kWh.

Memo 2

one W=one J/s=0.2388459 cal/s=859.8452 cal/h=0.8598 kcal/h;
one kW=one kJ/s=1000 J/s=238.8459 cal/s=859845.2279 cal/h=0.00085984523 Gcal/h;
one MW=one MJ/s=one million J/s=1000 kW=238845.8966 cal/s=0.85984523 Gcal/h;
one Gcal/h=one billion cal/h=1163000 W=1163 kW=1.163 MW=3968156 BTU/h;
one BTU/h=0.2931 W=0.0700017 cal/s=252.0062 cal/h=0.2520062 kcal/h;
one W=3.412 BTU/h, one kW=3412 BTU/h, one MW=3412000 BTU/h.

How is the BTU/h unit defined and what is it used for? 1 BTU is the amount of heat required to heat 1 pound of water 1° Fahrenheit (°F). This unit of measurement is mainly used to indicate the heat output of installations such as air conditioners.

Calculation examples

Here we come to the most important thing. How to convert one value to another using the above ratios? Everything is not so difficult. Let's look at this with examples.

Example 1

Thermal power of a copper - 30 kW. What is its equivalent power, expressed in Gcal / h?

Solution. Since 1 kW \u003d 0.00085984523 Gcal / h, then 30 kW \u003d 30 * 0.00085984523 Gcal / h \u003d 0.0257953569 Gcal / h.

Example 2

It is estimated that an air conditioner with a capacity of at least 2.5 kW is required to cool an office. For the purchase, an air conditioner with a capacity of 8000 BTU / h was chosen. Is there enough air conditioner power to cool the office?

Solution. Since 1 BTU/h=0.2931 W, then 8000 BTU/h=2344.8 W=2.3448 kW. This value is less than the calculated value of 2.5 kW, so the selected air conditioner is not suitable for installation.

Example 3

The heat supply organization supplied 0.9 Gcal of heat per month. What power should a radiator be installed so that it gives the same amount of heat per month?

Solution. Let's assume that heat was supplied to the house evenly over one month (30 days), so the heat output supplied by the boiler house can be found by dividing the entire amount of heat by the number of hours in a month: P = 0.9 Gcal / (30 * 24 h) \u003d 0.00125 Gcal / h. This power in terms of kilowatts will be equal to P \u003d 1163 kW * 0.00125 \u003d 1.45375 kW.

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