How to independently calculate the heat loss of a building. Calculation of heat losses to the surrounding space

Calculation of the heating system, hot water supply and ventilation

Explanatory note to the course work on the discipline

"Heating, ventilation and air conditioning"

Completed:

student of group 31 E

Zakharets A.V.

Supervisor

Art. teacher of the department T

Koksharov M.V.

According to the option you need:

1) Calculate the heat loss of the building.

3) Calculate the hot water supply system.

4) Draw an isometric diagram of the hot water supply system, indicate the diameters of the pipelines

5) Calculate the ventilation system, determine the amount of heat for heating the ventilated air.

UDC 621.313.333

The course work contains 28 pages, 7 figures, 4 tables, 5 sources, 2 applications.

Heat losses, enclosing structures, heating system, radiator, coolant, infiltration, hot water supply, riser, plank bed, pipeline, ventilation.

The object of study is a two-story residential building.

The purpose of the work is the development and consolidation of methods for calculating the heat losses of a building, heating systems, hot water supply, ventilation.

Research methods - calculation and graphic.

Coursework done in a text editor Microsoft Word 2007

Introduction. 5

1 Initial data. 6

2 Calculation of heat losses of the building. 7

2.1 Filling in the table.. 7

2.2 Calculation of the diameters of pipelines of the heating system. 20

3 Calculation DHW systems.. 23

3.1 Determination of the estimated water consumption in DHW systems .. 23

3.2 Determining the diameters of the DHW pipeline .. 23

4 Calculation of the ventilation system. 26

4.1 Consumption supply air. 26

4.2 Determination of heat consumption for heating ventilated air. 26

Conclusion. 28

Bibliographic list. 29

Annex A

Annex B

Introduction

The heat loss calculation is milestone design of heating, hot water and ventilation systems.

To determine the thermal power covering maximum load on the heating system, it is necessary to know the heat loss of the building in the most severe settlement part of the cold period of the year. To address the issue of compliance of the level of heat consumption by the heating system of the building with modern requirements, especially considering the problem of energy saving, it is necessary to determine the heat loss of the building for the entire heating period.

There are various approaches to choosing the calculated values ​​of the thermal conductivity coefficients building materials. At the same time, care in choosing the value given coefficient extremely important. It is also necessary to correctly evaluate the values ​​of the heat transfer coefficients on the surfaces of the fences, especially the heat transfer coefficient on inner surface, because if its value is too high, the calculated temperature on the inner surface, for example, of a window, will also be too high. When determining the heat loss of a building, it is important to correctly assess the heat transfer coefficients of the building envelope.

The paper presents calculations of the heat loss of the building and the need for heat for heating infiltration air, calculated and designed heating, hot water and ventilation systems.

The purpose of this work is to gain knowledge, skills in the calculation and design of heating, hot water and ventilation systems.

Initial data

Figure 1.1 - Plan of the first (second) floor of the building

Table 1.1 - Initial data

Calculation of building heat losses

With a careful approach to the design of a home heating system, it is necessary to start by calculating the heat loss of the building. Heat loss in the house occurs through walls, windows, entrance doors, roof and floor of the first floor. Heat also escapes with air when it infiltrates through gaps in structures, windows and doors.

For the convenience of calculating and presenting information, the result of the second section of this term paper the table will be filled. For each room, 25 parameters will be determined or calculated. The calculation is made in accordance with SNiP 23-02-2003 " Thermal protection buildings."

Filling in the table

2.1.1 Name of the room

This column indicates the room number according to the building plan. Usually the numbering of rooms starts from the entrance and goes clockwise. The first digit is the floor number, the rest are the room number.

Figure 2.1 - Plan of the first floor of the task

Figure 2.2 - Plan of the second floor of the task.

2.1.2 Outside air temperature.

In this column, in accordance with SNiP 23-01-99 "Construction climatology", the air temperature of the coldest five-day period with a security of 0.92 tn, ° C for the desired city or region is indicated.

For St. Petersburg t n \u003d -26 ° С

2.1.3 Design indoor air temperature

In this column, in accordance with GOST 30494-2011 "Residential and public buildings" indicates optimum temperature indoor air t in, ° C, depending on its type. Yes, for living rooms

t in \u003d 18 - 20 ° С, for bathrooms t in \u003d 24 - 26 ° С, for kitchens t in \u003d 19 - 21 ° С.

In calculations for bathrooms, we take t in = 25 ° C, for all other rooms t in = 20 ° C

2.1.4 Name of the surface.

The following abbreviations are introduced to designate enclosing structures:

HC - outer wall

TO - window

DN - outer door

2.1.5 Surface orientation

The orientation of the vertical enclosing structures to the cardinal points is indicated:

B - east

2.1.6 Surface length

The length or, in the case of a vertical surface, the height of the building envelope is indicated in meters.

2.1.7 Surface width

Specifies the width of the surface in meters.

2.1.8 Surface area

The surface area is defined as the product of the length (height) and the width of the surface according to the formula:

a – length (height), m

b - width, m

When calculating heat losses, the area of ​​individual fences A, m2, is determined in compliance with the following rules measurements:

1. The area of ​​windows, doors and lanterns is measured by the smallest building opening.

2. The area of ​​the ceiling and floor is measured between the axes of the inner walls and the inner surface of the outer wall. The area of ​​walls and floors located on the ground, including on logs, is determined with a conditional breakdown of them into zones.

3. The area of ​​the outer walls is measured

In plan - along the outer perimeter between the axes of the inner walls and the outer corner of the wall;

In height - on all floors except the lower one: from the level of the finished floor to the floor of the next floor. On the last floor the top of the outer wall coincides with the top of the cladding, or attic floor. On the lower floor, depending on the floor design: a) from the inner surface of the floor on the ground; b) from the preparation surface for the floor structure on the logs; c) from the lower edge of the ceiling over an unheated underground or basement.

4. When determining heat loss through internal walls their areas are measured along the inner perimeter. Heat loss through the internal enclosures of the premises can be ignored if the air temperature difference in these premises is 3°C or less.

The transfer of heat from the room through the structure of the floor or wall and the thickness of the soil with which they come into contact is subject to complex laws. To calculate the resistance to heat transfer of structures located on the ground, a simplified method is used. The floor surface on the ground is divided into strips 2 m wide, parallel to the junction of the outer wall and the ground surface. The counting of zones starts along the wall from the ground level, and if there are no walls along the ground, then zone I is the floor strip closest to the outer wall. The next two strips will be numbered II and III, and the rest of the floor will be zone IV. (see figure 2.3)

Thus, total area the floor is divided into zones and the area is entered in a column for each floor zone, and for the first zone, the area in the corners of the building is counted twice.

Figure 2.3 - The principle of dividing the floor of the building into zones

Figure 2.4 - Splitting the floor of the 1st floor into zones

2.1.9 Calculated temperature difference

,ºС is determined as the difference between the temperatures of the indoor air in the room and the temperature of the outdoor air of the coldest five-day period according to the formula:

(2.2)

2.1.10 Coefficient n

We choose the coefficient n, which takes into account the position of the building envelope in relation to the outside air:

n = 1. External walls and coverings (including those ventilated by outside air), attic floors (with a roof made of piece materials) and over driveways; ceilings over cold (without enclosing walls) undergrounds in the Northern building-climatic zone.

n = 0.9. Ceilings over cold cellars communicating with outside air; attic ceilings (with a roof made of roll materials); ceilings over cold (with enclosing walls) undergrounds and cold floors in the Northern building-climatic zone.

n=0.75. Ceilings over unheated basements with skylights in the walls.

n = 0.6. Ceilings over unheated basements without skylights in the walls, located above ground level.

n = 0.4. Ceilings over unheated technical undergrounds located below ground level

2.1.11 Heat transfer coefficient of the building envelope

The heat transfer coefficient of the enclosing structure k, W / (m 2 ∙ ° С) - a value numerically equal to surface density heat flow passing through the building envelope with a difference between the internal and outdoor temperature air is calculated by the formula:

where R i is the normative value of the heat transfer resistance of the i-th zone of the floor.

For each zone of an uninsulated floor, standard values heat transfer resistance:

zone I - R I \u003d 2.1 m 2 ° C / W;

zone II - R II \u003d 4.3 m 2 ° C / W;

zone III - R III \u003d 8.6 m 2 ° C / W;

zone IV - R IV \u003d 14.2 m 2 ° C / W.

2.1.12 Main heat losses

The formula for calculating the main heat loss Q main, W of the room through the building envelope:

where k is the heat transfer coefficient of the building envelope, W / (m 2 ∙ ° С);

A - surface area, m 2

2.1.13 Additional loss factor β 1

The addition to the orientation of the fence along the cardinal points is accepted for all external vertical fences or vertical projections of external inclined fences:

· for northern, northeastern, northwestern, eastern orientation ß 1 = 0.1;

southeastern and western ß 1 = 0.05;

southern and southwestern ß 1 = 0.

Figure 2.5 - The value of the coefficient ß 1

2.1.14 Additional loss factor β 2

The addition for a corner room with two or more external walls takes into account that the radiation temperature in such a room is lower than in a standard room. Therefore, in corner room in a residential building, the internal air temperature is taken 2 ° C higher than in an ordinary room, and in buildings for other purposes, increased heat losses are taken into account by adding ß 2 \u003d 0.05 to the main heat losses of vertical external fences.

2.1.15 Additional loss factor β 3

The addition to the penetration of cold air through external doors into a building that is not equipped with an air-thermal curtain, when they are opened for a short time, is taken into account as the main heat loss of the doors. So, in a building with a height H for triple doors with two vestibules , for double doors with tambour , for double doors without vestibule , for single doors . For external gates in the absence of a vestibule and air curtain heat losses are calculated with an additive, and if there is a vestibule at the gate - with an additive. The specified additives do not apply to summer and spare exterior doors and gates.

2.1.16 Total additional loss factor

The total coefficient of additional losses is determined by the formula:

2.1.17 Heat losses taking into account additional losses Q β

To find heat losses, taking into account additional losses, it is necessary to multiply the values ​​of the twelfth and sixteenth columns, i.e. the influence of additional coefficients on the main heat losses is taken into account.

2.1.18 Rated air permeability

Rated air permeability G n is the maximum permitted air permeability of the structure for any weather conditions, taken in accordance with SNiP 23-02-2003, the values ​​​​of which are given in table. 2.1

Table 2.1 - Values ​​G n

2.1.19 Air pressure difference

The flow rate of outdoor air entering the premises as a result of infiltration under design conditions depends on the space-planning solution of the building, as well as the density of windows, balcony doors, and stained-glass windows. The task of engineering calculation is reduced to determining the flow rate of infiltration air G inf, kg / h, through separate fences of each room. Infiltration through walls and coverings is small, so it is usually neglected and calculated only through the filling of skylights, as well as through closed doors and gates, including those that, under normal operating mode do not open. The heat costs for air rushing in through opening doors and gates in the design mode are taken into account as additions to the main heat losses through the entrance doors and gates.

The calculation reveals the maximum possible infiltration, so each window or door is considered to be on the windward side of the building.

The calculated pressure difference Δp, Pa for a window or door of each floor is determined by the formula:

For doors:

(2.9)

R inf.ok R inf.dv - the required resistance to air penetration of the window and door, respectively, m 2 ∙ h / kg;

Δр – calculated pressure difference, Pa;

Δр 0 – 10 Pa.

2.1.21 Infiltration heat transfer coefficient

Coefficient taking into account the influence of transmission heat flow:

k = 0.7. For wall butt panels and for triple-glazed windows;

k = 0.8. For windows and balcony doors with separate bindings;

k = 1. For windows and balcony doors with paired or adjacent sashes.

2.1.22 Heat consumption for infiltration

Heat consumption for infiltration Q inf, W is calculated by the formula:

2.1.24 Power of the heater unit

As heater cast-iron radiator M-140, which is widely known in the CIS, was chosen. Cast iron sectional radiators are traditional appliances for our country.

Their main advantage is the ability to use open systems. Unlike other radiators, cast iron ones are practically insensitive to system emptying, that is, they allow you to drain water from it as often as you like. When cast iron is poured on its surface, a particularly durable layer with high content silicon, therefore, in the raw form, cast iron is quite resistant to corrosion, including from the effects of solid particles present in the coolant. Speaking of performance cast iron radiators, it should be noted their high thermal conductivity and large thermal inertia.

Radiator sections are cast from gray cast iron, they can be combined into devices of various sizes. Sections are connected on nipples with gaskets made of cardboard, rubber or paronite.

Let's take the power of one section of the M-140 radiator equal to 140 watts.

There is no heating in the bathroom. The room is heated by installing a heated towel rail on the DHW pipeline. Let's take the power of the heated towel rail equal to 260 watts.

2.1.25 Number of heating appliances

In order to find the number of sections of the M-140 radiator for one room, you need to divide the total heat loss of this room by the power of one section of the M-140 radiator.

General thermal load the first floor of the building is 25.152 kW, the second floor is 23.514 kW.

All calculations of the previous paragraphs are performed for each floor of the building and are tabulated in Appendix A (for the first floor) and Appendix B (for the second floor)

HEAT LOSS CALCULATION

UNINSULATED PIPING

FOR ABOVE-GROUND LAYING

METHODOLOGICAL INSTRUCTIONS

Introduction

This document discusses the features of calculating heat losses by uninsulated pipelines of heat networks during above-ground laying and proposes a practical method for performing the calculation.

The calculation of heat losses by insulated pipelines must be carried out in accordance with the methods set forth in the current normative documents/12/. Characteristic for this situation is that the heat flow is mainly determined by the thermal resistance of the thermal insulation. In this case, the heat transfer coefficient on the outer surface of the cover layer has little effect on the amount of heat loss and, therefore, can be taken according to average values.

The operation of a heating network pipeline without thermal insulation is an atypical situation, since, according to the norms, all heat pipelines must have thermal insulation in order to avoid significant heat losses. That is why no regulatory documents provide methods for calculating the heat loss of pipelines for this case.

However, during the operation of heat networks, situations can and do arise when separate sections pipelines are deprived of thermal insulation. To ensure the possibility of calculating heat losses by such pipelines, this method has been developed. It is based on the most general theoretical dependencies for the heat transfer of a pipeline under conditions of forced convection, which are given in educational and reference literature.

According to customer's requirement, all formulas and calculated values are given not in the international system of units, but in relation to the measurement of heat loss in kcal/hour.

1. Theoretical basis heat loss calculation

uninsulated pipelines

with above-ground laying

The pipeline of the heating network is a horizontally located heated pipe, blown by the wind or located in calm air. Therefore, the heat transfer of such a pipeline can be determined from known dependencies using the heat transfer coefficient through the pipe wall:

Q = Fp · (Tp - Tv) / K, (1.1)

K = 1 / (1/αp + δm/λm + 1/αw), (1.2)

As the calculated temperatures, the average temperatures for the period under consideration should be taken. At the same time, the pipeline surface temperature can be taken equal to the water temperature in the pipeline, since the thermal resistance of the pipe wall δm/λm and resistance to heat transfer on the inner surface 1/αw for a clean pipe, many times less than the resistance to heat transfer on the outer surface 1/αp . This assumption makes it possible to significantly simplify the calculation and reduce the number of required initial data, since then it is not required to know the water velocity in the pipe, the pipe wall thickness, and the degree of wall contamination on the inner surface. The calculation error associated with such a simplification is small and much less than the errors associated with the uncertainty of other calculated values.

The area of ​​the outer surface of the pipeline is determined by its length and diameter:

Fp = π Dp L, (1.3)

Taking into account the above, expression (1) can be converted to the form:

Q = αp π Dp L (Tp - Tv), (1.4)

The most important thing in calculating heat losses is the correct determination of the heat transfer coefficients on the outer surface of the pipeline. The issue of heat transfer from a single pipe is well studied, and the calculated dependences are given in textbooks and reference books on heat transfer. According to the theory, the total heat transfer coefficient is defined as the sum of the convective and radiant heat transfer coefficients:

αp = αk + αl (1.5)

The coefficient of convective heat transfer depends on the air velocity and flow direction with respect to the axis of the pipeline, the diameter of the pipeline, and the thermophysical characteristics of the air. In the general case, the expression for determining the heat transfer coefficient on the outer surface of the pipeline with transverse airflow will be:

in the laminar mode of air movement (Reynolds criterion Re less than 1000)

αc = 0.43 βφ Re0.5 λv / Dn (1.6)

In the transitional and turbulent regime of air movement (Reynolds criterion Re equal to or greater than 1000)

αc = 0.216 βφ Re0.6 λv / Dn , (1.7)

Re = U β u Dn/v in , (1.8)

Choose a city Choose a city Brest Vitebsk Volgograd Dnepropetrovsk Yekaterinburg Zaporozhye Kazan Kyiv Lugansk Lvov Minsk Moscow Nizhny Novgorod Novosibirsk Odessa Omsk Perm Riga Rostov-on-Don Samara St. Petersburg Simferopol Ufa Kharkiv Chelyabinsk Chernigov t out = - o C

Enter the air temperature in the room; t ext = + o C

Heat loss through walls expand collapse

Heat loss through windows expand collapse

Heat loss through ceilings expand collapse

Heat loss through the floor expand collapse