Water speed and return temperature in the heating system

Heat meters

Let us remember once again that the heat supply network of an apartment building is equipped with thermal energy metering units, which record both the gigacalories consumed and the cubic capacity of water passed through the intra-house line.

In order not to be surprised by bills containing unrealistic amounts for heat when the degrees in the apartment are below normal, before the start of the heating season, check with the management company whether the meter is in working condition and whether the verification schedule has been violated.

Many manufacturers of boiler equipment require that at the entrance to the boiler there be water at least a certain temperature, since cold return water has a bad effect on the boiler:

boiler efficiency decreases,
condensation on the heat exchanger increases, which leads to corrosion of the boiler,
Due to the large temperature difference at the inlet and outlet of the heat exchanger, its metal expands differently - hence the stress and possible cracking of the boiler body.

The first method is ideal, but expensive.
Esbe
offers a ready-made module for mixing into the boiler return and controlling the loading of the heat accumulator (relevant for solid fuel boilers) - the LTC 100 device is an analogue of the popular Laddomat unit.

Phase 1. Beginning of the combustion process. The mixing device allows you to quickly increase the boiler temperature, thus starting water circulation only in the boiler circuit.

Phase 2: Start loading the storage tank. The thermostat, opening the connection from the storage tank, sets the temperature, which depends on the version of the product. High, guaranteed return temperature to the boiler, maintained through the entire combustion cycle

Phase 3: Storage tank during loading. Good control ensures efficient loading of the storage tank and correct stratification within it.

Phase 4: The storage tank is fully loaded. Even at the final stage of the combustion cycle, the high quality of regulation ensures good control of the return temperature to the boiler while simultaneously fully loading the storage tank

Phase 5: End of combustion process. By completely closing the top opening, the flow is directly directed into the storage tank, using the heat in the boiler

The second method is simpler, using a high quality three-way thermomixing valve.

For example valves from ESBE or VTC300. These valves vary depending on the power of the boiler used. VTC300 is used for boiler power up to 30 kW, VTC511 and VTC531 - for more powerful boilers from 30 to 150 kW

The valve is mounted on the bypass line between the boiler flow and return.

The built-in thermostat opens input “A” when the temperature at output “AB” is equal to the thermostat setting (50, 55, 60, 65, 70 or 75°C). Input “B” closes completely when the temperature at inlet “A” exceeds the nominal opening temperature by 10°C.

When the coolant temperature at the outlet of valve “AB” is less than 61°C, inlet “A” is closed, and hot water flows through inlet “B” from the boiler supply to the return. If the temperature of the coolant at the outlet “AB” exceeds 63°C, the bypass input “B” is closed and the coolant from the system return flows through inlet “A” into the boiler return. Bypass output “B” opens again when the temperature at outlet “AB” drops to 55°C

When a coolant with a temperature of less than 61°C passes through the “AB” outlet, the “A” input from the system return is closed, and the hot coolant from the bypass “B” is supplied to the “AB” output. When the temperature at the outlet “AB” reaches more than 63°C, inlet “A” opens and water from the return is mixed with water from bypass “B”. To equalize the bypass (so that the boiler does not constantly operate in a small circulation circle), a balancing valve must be installed in front of the “B” inlet on the bypass.

Heating pipe temperature table

The heating temperature, including return pipes, directly depends on the readings of street thermometers . The colder the air outside and the higher the wind speed, the higher the cost of heat.

A standard table has been developed that reflects the temperature values at the inlet, supply and outlet of the coolant in the heating system. The indicators presented in the table provide comfortable conditions for a person in a living space:

Pace. external, °С	+8	+5	+1	-1	-2	-5	-10	-15	-20	-25	-30	-35
Pace. at the entrance	42	47	53	55	56	58	62	69	76	83	90	97	104
Pace. radiators	40	44	50	51	52	54	57	64	70	76	82	88	94
Pace. return lines	34	37	41	42	43	44	46	50	54	58	62	67	69

Important! the difference between the supply and return temperatures depends on the direction of movement of the coolant. If the wiring is from above, the differences are no more than 20°C , if from below - 30°C.

Briefly about return and flow in the heating system

The water heating system, using a supply from the boiler, supplies heated coolant to the radiators, which are located inside the building. This makes it possible to distribute heat throughout the house. Then the coolant, that is, water or antifreeze, having passed through all available radiators, loses its temperature and is supplied back for heating.

The most simple heating structure consists of a heater, two lines, an expansion tank and a set of radiators. The conduit through which heated water from the heater moves to the batteries is called the supply. And the water conduit, which is located at the bottom of the radiators, where the water loses its original temperature and returns back, will be called return. Since water expands when heated, the system provides a special tank. It solves two problems: a supply of water to saturate the system; accepts excess water, which is obtained during expansion. Water, as a heat carrier, is directed from the boiler to the radiators and back. Its flow is ensured by a pump, or natural circulation.

Supply and return are present in one and two pipe heating systems. But in the first there is no clear distribution into the supply and return pipes, and the entire pipe line is conditionally divided in half. The column that leaves the boiler is called the supply, and the column that comes out from the last radiator is called the return.

In a single-pipe line, heated water from the boiler flows sequentially from one battery to another, losing its temperature. Therefore, at the very end the batteries will be the coldest. This is the main and probably the only disadvantage of such a system.

But the single-pipe version will have more advantages: lower costs for purchasing materials are required compared to a 2-pipe; the diagram looks more attractive. It is easier to hide the pipe, and you can also lay pipes under doorways. The two-pipe system is more efficient - two fittings are installed in parallel into the system (supply and return).

This system is considered more optimal by experts. After all, its work revolves around supplying hot water through one pipe, and cooled water is discharged in the opposite direction through another pipe. In this case, the radiators are connected in parallel, which ensures uniform heating. Which of them establishes the approach must be individual, taking into account many different parameters.

There are only a few general tips to follow:

The entire line must be completely filled with water; air is a hindrance; if the pipes are airy, the heating quality is poor.
It is necessary to maintain a sufficiently high fluid circulation rate.
The difference in supply and return temperatures should be about 30 degrees.

How do supply and return temperatures affect heat consumption in an apartment building?

The only way out in this situation is a more correct redistribution between the risers. And for this, the risers need to be balanced with each other. This should be done by balancing valves (valves) that need to be installed on the return lines of the risers. In the hydraulic diagram shown above, as an example, balancing valves VALTEC, vT.054, DN20 are used (valves of other brands can also be used).

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As mentioned earlier, airing the system is inevitable. The only way to prevent air from entering the system is to start it up correctly. However, the remaining factors described at the beginning of the article are enough for air pockets to appear in the system. Therefore, it is more advisable to give some tips on how to make it easier to eliminate air jams.

Optimal values in an individual heating system

Autonomous heating helps to avoid many problems that arise with a centralized network, and the optimal temperature of the coolant can be adjusted according to the season. In the case of individual heating, the concept of standards includes the heat transfer of a heating device per unit area of the room where this device is located. The thermal regime in this situation is ensured by the design features of the heating devices.

It is important to ensure that the coolant in the network does not cool below 70 °C. 80 °C is considered optimal

With a gas boiler, it is easier to control heating, because manufacturers limit the ability to heat the coolant to 90 °C. Using sensors to regulate the gas supply, the heating of the coolant can be adjusted.

It is a little more difficult with solid fuel devices; they do not regulate the heating of the liquid, and can easily turn it into steam. And it is impossible to reduce the heat from coal or wood by turning the knob in such a situation. Control of heating of the coolant is quite conditional with high errors and is carried out by rotary thermostats and mechanical dampers.

Electric boilers allow you to smoothly regulate the heating of the coolant from 30 to 90 °C. They are equipped with an excellent overheat protection system.

Heating system design, what is return

The heating system consists of an expansion tank, batteries, and a heating boiler. All components are connected to each other in a circuit. A coolant liquid is poured into the system. The liquid used is water or antifreeze. If the installation is done correctly, the liquid is heated in the boiler and begins to rise through the pipes. When heated, the liquid increases in volume, the excess enters the expansion tank.

Since the heating system is completely filled with liquid, the hot coolant displaces the cold coolant, which returns to the boiler, where it is heated. Gradually, the temperature of the coolant increases to the required temperature, heating the radiators. Liquid circulation can be natural, called gravitational, or forced, using a pump.

The return is a coolant that, having passed through all the heating devices included in the circuit, gives up its heat and, cooled, enters the boiler again for the next heating.

Batteries can be connected in three ways:

1. Bottom connection.
2. Diagonal connection.
3. Lateral connection.

In the first method, the coolant is supplied and the return is discharged at the bottom of the battery. This method is advisable to use when the pipeline is located under the floor or baseboards. With a diagonal connection, the coolant is supplied from above, the return is discharged from the opposite side from below. This connection is best used for batteries with a large number of sections. The most popular method is side connection. The hot liquid is connected from above, the return is discharged from the bottom of the radiator on the same side where the coolant is supplied.

Heating systems differ in the way pipes are laid. They can be laid in one-pipe or two-pipe ways. The most popular is the single-pipe wiring diagram. Most often it is installed in multi-storey buildings. It has the following advantages:

a small number of pipes;
low cost;
ease of installation;
serial connection of radiators does not require the organization of a separate riser for liquid drainage.

Disadvantages include the inability to adjust the intensity and heating for a separate radiator, and a decrease in the temperature of the coolant as it moves away from the heating boiler. To increase the efficiency of single-pipe distribution, circular pumps are installed.

To organize individual heating, a two-pipe pipe layout is used. Hot feed is carried out through one pipe. In the second, cooled water or antifreeze flows back into the boiler. This scheme makes it possible to connect radiators in parallel, ensuring uniform heating of all devices. In addition, the two-pipe circuit allows you to regulate the heating temperature of each heating device separately. The disadvantage is the complexity of installation and the high consumption of materials.

Central heating

How does an elevator unit work?

At the elevator entrance there are valves that cut it off from the heating main. Along their flanges closest to the wall of the house, there is a division of areas of responsibility between homeowners and heat suppliers. The second pair of valves cuts off the elevator from the house.

The supply pipe is always at the top, the return pipe is always at the bottom. The heart of the elevator unit is the mixing unit, in which the nozzle is located. A stream of hotter water from the supply pipe flows into the water from the return pipe, drawing it into a repeated circulation cycle through the heating circuit.

By adjusting the diameter of the hole in the nozzle, you can change the temperature of the mixture entering the.

Strictly speaking, an elevator is not a room with pipes, but this unit. In it, supply water is mixed with return water.

What is the difference between the supply and return pipelines of the route?

In normal operation it is about 2-2.5 atmospheres. Typically, 6-7 kgf/cm2 enters the house on the supply side and 3.5-4.5 on the return side.

What is the difference in the heating system

The difference on the highway and the difference in the heating system are two completely different things. If the return pressure before and after the elevator does not differ, then instead of supply, a mixture is supplied to the house, the pressure of which exceeds the readings of the pressure gauge on the return by only 0.2-0.3 kgf/cm2. This corresponds to a height difference of 2-3 meters.

This difference is spent to overcome the hydraulic resistance of bottlings, risers and heating devices. Resistance is determined by the diameter of the channels through which water moves.

What diameter should be the risers, fillers and connections to radiators in an apartment building?

The exact values are determined by hydraulic calculation.

In most modern houses the following sections are used:

Heating outlets are made from pipes DN50 - DN80.
For risers, a pipe DN20 - DN25 is used.
The connection to the radiator is made either equal to the diameter of the riser, or one step thinner.

The photo shows a more sensible solution. The diameter of the liner is not underestimated.

What to do if the return temperature is too low

In such cases:

The nozzle is drilled out
. Its new diameter is agreed with the heat supplier. An increased diameter will not only raise the temperature of the mixture, it will also increase the drop. The circulation through the heating circuit will speed up.
In the event of a catastrophic lack of heat, the elevator is disassembled, the nozzle is removed, and the suction (pipe connecting the supply to the return) is turned off. The heating system receives water directly from the supply pipe. Temperature and pressure drop increase sharply.

What to do if the return temperature is too high

The standard measure is to weld the nozzle and re-drill it, with a smaller diameter.
When an urgent solution is needed without stopping the heating, the difference at the entrance to the elevator is reduced with the help of shut-off valves. This can be done with an inlet valve on the return line, controlling the process using a pressure gauge. This solution has three disadvantages:
- The pressure in the heating system will increase. After all, we limit the outflow of water; the lower pressure in the system will become closer to the supply pressure.
There is always the possibility of worn cheeks falling. If they completely shut off the water, the heating (primarily the access heating) will defrost within two to three hours.

Why do you need high pressure in the line?

Indeed, in private houses with autonomous heating systems, an excess pressure of only 1.5 atmospheres is used. And, of course, more pressure means much higher costs for stronger pipes and power supply for injection pumps.

The need for greater pressure is associated with the number of floors in apartment buildings. Yes, circulation requires a minimum drop; but the water needs to be raised to the level of the jumper between the risers. Each atmosphere of excess pressure corresponds to a water column of 10 meters.

Knowing the pressure in the line, it is not difficult to calculate the maximum height of a house that can be heated without the use of additional pumps. The calculation instructions are simple: 10 meters multiplied by the return pressure. A return pipeline pressure of 4.5 kgf/cm2 corresponds to a water column of 45 meters, which, with a height of one floor of 3 meters, will give us 15 floors.

By the way, hot water supply in apartment buildings is supplied from the same elevator - from the supply (at a water temperature of no higher than 90 C) or return. If there is a lack of pressure, the upper floors will remain without water.

How to control the pressure in the system?

To control, pressure gauges are installed at various points of the heating system, and (as mentioned above) they record excess pressure. As a rule, these are deformation devices with a Bredan tube. If you need to take into account the fact that the pressure meter must work not only for visual control, but also in the automation system, electric contact or other types of sensors are used.

The insertion points are determined by regulatory documents, but even if you have installed a small boiler for heating a private house, which is not controlled by GosTechnadzor, it is still advisable to use these rules, since they highlight the most important points of the heating system for pressure control.

Pressure gauges must be installed through three-way valves, which ensure their purging, reset to zero and replacement without stopping the entire heating.

Control points are:

Before and after the heating boiler;
Before the entrance and after the circulation pumps;
Output of heating networks from a heat generating unit (boiler house);
Input of heating into the building;
If a heating regulator is used, then pressure gauges are embedded before and after it;
If there are mud traps or filters, it is advisable to install pressure gauges before and after them. Thus, it is easy to control their contamination, taking into account the fact that a working element creates almost no difference.

System with installed pressure gauges
A symptom of malfunctions or improper operation of the heating system are pressure surges. What do they mean?

How to make radiators hot, looking for solutions

If you find that the return is too cold, you should take a number of steps to find the causes and troubleshoot problems. First of all, you need to check that the connection is correct. If the connection is not made correctly, the down pipe will be hot when it should be slightly warm. The pipes should be connected according to the diagram.

To avoid air pockets that impede the flow of coolant, it is necessary to provide for the installation of a Mayevsky valve or bleeder for air removal. Before bleeding the air, you need to turn off the supply, open the tap and let out the air. Then the tap is turned off and the heating valves open.

Often the cause of cold return is the control valve: the cross-section is narrowed. In this case, the tap must be dismantled and the cross-section increased using a special tool. But it is better to buy a new faucet and replace it.

The reason may be clogged pipes. You need to check them for passability, remove dirt and deposits, and clean them well. If passability cannot be restored, the clogged areas should be replaced with new ones.

If the coolant flow rate is insufficient, you need to check whether there is a circulation pump and whether it meets the power requirements. If it is missing, it is advisable to install it, and if there is a lack of power, replace or upgrade it.

Knowing the reasons why heating may not work efficiently, you can independently identify and eliminate malfunctions. Comfort in the house during the cold season depends on the quality of heating. If you carry out the installation work yourself, you can save on hiring third-party labor.

When autumn confidently strides across the country, snow is flying above the Arctic Circle, and in the Urals night temperatures stay below 8 degrees, then the word form “heating season” sounds appropriate. People remember past winters and try to understand the normal temperature of the coolant in the heating system.

Prudent owners of individual buildings carefully inspect the valves and nozzles of boilers. By October 1, residents of an apartment building are waiting like Santa Claus for a plumber from the management company. The Lord of valves and valves brings warmth, and with it joy, fun and confidence in the future.

What does a large or small pressure difference between flow and return mean?

The normal difference between the pressure of the supply and return pipelines is 1-2 atmospheres. What does a change in this value in one direction or the other mean?

If the difference between the supply and return pressure is significant, then the system is almost at a standstill, possibly due to an air lock. It is necessary to find the cause and restore coolant circulation;
If in the heating system of your home it is significantly less and tends to zero, then the movement of water through the pipes is disrupted. Most likely, water flows through nearby areas and does not reach distant areas; the regulation is broken. But you also need to take into account that if the difference changes over time, and all the radiators warm up normally, the heating regulator may be to blame - the principle of its operation includes bypassing part of the water from the supply to the return, and perhaps the jump is due to the fact that just this cycle.

What is the difference between heating flow and return?

And so, let’s summarize the differences between supply and return in heating:

Supply – coolant that flows through water pipes from a heat source. This could be an individual boiler or central heating of the house.
Return water is water that, having passed through all the heating radiators, goes back to the heat source. Therefore, at the input of the system there is supply, and at the output there is return.
It also differs in temperature. The feed is hotter than the return.
Installation method. The water conduit that is attached to the top of the battery is the supply; the one that connects to the bottom is the return line.

If there is a large temperature difference between the boiler supply and return, the temperature on the walls of the boiler combustion chamber approaches the “dew point” temperature and condensation may form. It is known that during the combustion of fuel various gases are released, including CO 2; if this gas combines with the “dew” that has fallen on the walls of the boiler, an acid is formed that corrodes the “water jacket” of the boiler furnace. As a result, the boiler can quickly fail. To prevent dew, it is necessary to design the heating system so that the temperature difference between the supply and return is not too large. This is usually achieved by heating the return coolant and/or including a hot water supply boiler in the heating system with soft priority.

To heat the coolant between the return and the boiler supply, a bypass is made and a circulation pump is installed on it. The power of the recirculation pump is usually chosen as 1/3 of the power of the main circulation pump (sum of pumps) (Fig. 41). To prevent the main circulation pump from “pushing” the recirculation circuit in the opposite direction, a check valve is installed behind the recirculation pump.

Rice. 41. Return heating

Another way to heat the return is to install a hot water boiler in close proximity to the boiler. The boiler is “placed” on a short heating ring and positioned in such a way that hot water from the boiler after the main distribution manifold immediately enters the boiler, and from it returns back to the boiler. However, if the need for hot water is small, then both a recirculation ring with a pump and a heating ring with a boiler are installed in the heating system. With proper calculation, the recirculation pump ring can be replaced with a system with three- or four-way mixers (Fig. 42).

Rice. 42. Heating the return using three- or four-way mixers On the pages “Regulating equipment of heating systems” almost all technically significant devices and engineering solutions present in classic heating circuits were listed. When designing heating systems on real construction sites, they must be fully or partially included in the design of heating systems, but this does not mean that exactly the heating fittings that are indicated on these pages of the site should be included in a specific project. For example, at the recharge unit you can install shut-off valves with check valves built into them, or you can install these devices separately. Instead of mesh filters, you can install dirt filters. You can install an air separator on the supply pipelines, or you can not install it, but instead install automatic air vents in all problem areas. You can install a deslimer on the return line, or you can simply equip the collectors with drains. Adjustment of the coolant temperature for underfloor heating circuits can be done with qualitative adjustment using three- and four-way mixers, or quantitative adjustment can be made by installing a two-way valve with a thermostatic head. Circulation pumps can be installed on a common supply pipe or vice versa, on the return pipe. The number of pumps and their location may also vary.

How do supply and return temperatures affect heat consumption in an apartment building?

1. “Spitting against the wind” Open SNIP Heat Supply, find the section that indicates the temperature of the coolant (min max) and you will receive regulatory proof. Contact your heating network so that they can provide you with a “heat supply temperature schedule” for your building. There will be a table with several outside air temperatures and the corresponding supply and return temperatures. If according to this schedule there is a discrepancy with the supply to your heating unit, then you can make a fuss and file a lawsuit against them demanding moral compensation and an increase in coolant parameters.

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The heating network supplies coolant to consumers (for heating houses) according to the temperature schedule. Those. Depending on the outside air temperature, the boiler room operator must regulate the temperature at the outlet of the boiler room. And according to this temperature schedule, the designer must select the required number of heating devices (radiators, batteries) and their size (radiator length or number of sections).

Calculation of heating operating temperature conditions

When calculating heat supply, it is necessary to take into account the properties of all components. This is especially true for radiators. What is the optimal temperature for heating radiators - +70°C or +95°C? It all depends on the thermal calculation, which is performed at the design stage.

An example of drawing up a heating temperature schedule

First, it is necessary to determine the heat losses in the building. Based on the data obtained, a boiler with the appropriate power is selected. Then comes the most difficult design stage - determining the parameters of the heat supply batteries.

They must have a certain level of heat transfer, which will affect the temperature chart of the water in the heating system. Manufacturers indicate this parameter, but only for a certain operating mode of the system.

If to maintain a comfortable level of air heating in a room you need to spend 2 kW of thermal energy, then the radiators must have a no less heat transfer rate.

To determine this, you need to know the following quantities:

The maximum permissible water temperature in the heating system is t1. It depends on the power of the boiler, the temperature limit on the pipes (especially polymer ones);
The optimal temperature that should be in the heating return pipes is t This is determined by the type of pipeline layout (one-pipe or two-pipe) and the total length of the system;
The required degree of heating of the air in the room is t.

Having these data, you can calculate the temperature difference of the battery using the following formula:

Next, to determine the power of the radiator, use the following formula:

Where k is the heat transfer coefficient of the heating device. This parameter must be indicated in the passport; F – radiator area; Tnap – thermal pressure.

By varying various indicators of the maximum and minimum water temperatures in the heating system, you can determine the optimal operating mode of the system

It is important to correctly initially calculate the required power of the heating device. Most often, the low temperature indicator in heating radiators is associated with heating design errors

Experts recommend adding a small margin to the obtained radiator power value - about 5%. This will be needed if the outside temperature drops critically in winter.

Most manufacturers indicate the heat output of radiators according to accepted standards EN 442 for mode 75/65/20. This corresponds to the normal heating temperature in the apartment.

Why do you need a differential pressure regulator?

For the normal functioning of the heating system and stable circulation of water through all its elements, a stable pressure drop is required. Sudden surges in coolant pressure lead to disruption of the hydraulic regime and incorrect operation of individual components.

Diaphragm expander

In the heating system of a small house, as a rule, membrane water accumulators are installed, which allow you to get rid of these undesirable phenomena. In more complex and larger systems, a regulator is used that ensures a stable pressure drop in the heating system and avoids airing even during sudden surges in the main pipelines. Also, the regulator is often mounted on the bypass (bypass) lines of pumps, which makes it possible to make the characteristics of the unit constant.

And finally, a video about how NOT to do it - first the calculation is done, and only then the implementation, and not vice versa:

The reliability and performance of a heating system depends on the efficient operation of all parts included in it.

These include : a boiler for heating the coolant, radiators connected to it and to each other in a certain way, an expansion tank, a circulation pump, shut-off and control valves, and a pipeline of the required diameter.

Creating highly efficient heating system is possible thanks to special knowledge and experience in this field of activity. An important role in the working process of heating a room is played by the return pipeline.

Ways to reduce heat loss

The above information will help to be used to correctly calculate the coolant temperature norm and tell you how to determine situations when you need to use a regulator.
But it is important to remember that the temperature in the room is affected not only by the temperature of the coolant, street air and wind strength. The degree of insulation of the facade, doors and windows in the house should also be taken into account

To reduce heat loss from your home, you need to worry about its maximum thermal insulation. Insulated walls, sealed doors, and metal-plastic windows will help reduce heat loss. This will also reduce heating costs.

First, let's look at a simple diagram:

In the diagram we see a boiler, two pipes, an expansion tank and a group of heating radiators. The red pipe through which hot water flows from the boiler to the radiators is called DIRECT. And the lower (blue) pipe through which colder water returns is called REVERSE. Knowing that when heated, all bodies expand (including water), an expansion tank is built into our system. It performs two functions at once: it is a reserve of water to replenish the system and excess water goes into it during expansion from heating. Water in this system is a coolant and therefore must circulate from the boiler to the radiators and back. Either a pump or, under certain conditions, the force of earth's gravity can force it to circulate. If everything is clear with the pump, then with gravity many may have difficulties and questions. We have dedicated a separate topic to them. For a deeper understanding of the process, let's look at the numbers. For example, the heat loss of a house is 10 kW. The operating mode of the heating system is stable, that is, the system neither warms up nor cools down. The temperature in the house does not rise or fall. This means that 10 kW is generated by the boiler and 10 kW is dissipated by the radiators. From a school physics course we know that to heat 1 kg of water by 1 degree we will need 4.19 kJ of heat. If we heat 1 kg of water by 1 degree every second, then we will need power

G=Q/(4.19dT)=10/(4.1910)=0.24 kg/sec.

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