HU184156B - Method for determining the consistency of thermal insulation and the heat loss of duct at operating distance heating duct laid in concrete chanell - Google Patents

Abstract

By the method of the invention, it is possible to determine the actual heat loss of an operating heat pipe without prior exploration, from which it is possible to determine the quality of the thermal insulation of the line and to decide whether it is necessary to renovate the insulation. The method according to the invention is to drill a hole in the concrete channel cover to measure the depth of the concrete channel and the temperature of the concrete channel cover, and to determine the value of the actual heat loss per unit of loss by means of two characteristics. Using the documented design features of district heating: the heat loss calculation methods are known in the art using known heat loss calculation methods. If the value of the actual heat loss differs from the value of the theoretical heat loss, if it is greater than the theoretical loss, it indicates the degree of deterioration of the thermal insulation of the conductor and the thermal resistance of the insulation. -1-

Description

The majority of the losses of district heating systems is the heat loss of the pipes laid in the reinforced concrete duct. This heat loss is greatly increased if during the operation, due to groundwater intrusion, aging or other effects, the thermal insulation of the pipe is degraded. Soaked thermal insulation causes rapid corrosion, which can be a source of serious malfunctions.

The operators of district cooling systems as an important interests _(s to recognize relative district heating networks in various real-period operating loss of heat and the texture of each section of the insulation.

Without knowing the heat loss of the plant, the energy balance necessary for energy management cannot be prepared, and the impact of individual energy saving measures cannot be judged with sufficient accuracy.

Accurate knowledge of heat loss is also required to account for individual consumers through heat metering. The cost-effectiveness of the measures taken to enhance thermal protection can only be determined by comparing deteriorated and new thermal insulation.

You need to know how to repair each section of pipe and insulation, as well as planned preventive maintenance! the consistency of the existing insulation.

There is no practical solution for quantifying the real operational heat loss of district heating pipes and the deterioration of insulation.

The heat loss of district heating systems cannot be determined by direct measurement with acceptable accuracy. Known calculation methods only take into account design data and design thermal insulation quality.

Although in some cases thermal degradation of the insulation can be observed by thermal vision, the extent of degradation cannot be quantified. At present, the quality of insulation can only be ascertained by costly opening of the district heating pipeline and direct inspection of the insulation.

In accordance with the process of the present invention, the insulation quality of the district heating pipeline can be quantified in an easily practicable manner without exploration, and the heat loss of the operating section of the pipeline can be determined with sufficient accuracy.

The essence of the process according to the invention can be summarized as follows:

At least three soil samples are taken at different depths in at least three locations along the geometric centerline of the operating feed pipe section laid in the concrete channel. At least one 10 cm long soil sample shall be removed from the soil surface at each sampling site, and from the middle of the ground layer covering the concrete channel and directly above the concrete channel cover. The location of the soil sampling site should preferably be located so that it is located in the middle and at the two ends of the pipeline section in question. Care must be taken during the sampling to maintain the consistency of the soil. After sampling, the thermal conductivity of the soil samples is determined.

Soil samples are conductive! of the soil, calculate the average heat transfer coefficient Xt of the soil by arithmetic mean formation. Then, a hole is deepened between the sampling points in the concrete channel cover ice, the concrete channel depth H is measured, and a temperature sensor is placed on the cover to measure the real, undisturbed surface temperature of the cover. Therefore, the sensor should be insulated from the top to the extent of the heat resistance of the soil. Together with the positioning of the sensor, a temperature measuring and recording circuit is formed. After formation of the loop series of measurements is carried out for 24 hours continuously, or at least an hour is recorded in the concrete channel in which the t _w felü5 lations temperature and the arithmetic average of the values recorded formation is calculated at the average _w betoncsatornafedlap temperature.

During the same time period, the surface temperature tt of the conduit and other sources of heat and _the flow of water t _e , t _v _ _v H, free of line effects and other heat sources, are also recorded or measured and the mean values t _t , t _e and t _{v are determined} .

Using the depth H and the average heat transfer coefficient X _{t of} the soil, calculate the heat resistance R _{t of} the soil using the following formula:

- ¹ _ m__3AH__ _a_ - _ a »· ²⁵ · b« U5 '

2t> '(1) a = outer width of the channel section, b - external height of the channel section.

Then, using the approximate circumferential ke25 of the concrete channel as the temperature isotherm, we calculate the actual heat loss per unit length q of the district heating pipe using the formula:

^Q Rt (t _w - tt) · (2)

This heat loss refers to the actual operating parameters averaged over a 24 hour period.

These same operating parameters, the wireless terve35-life characteristics of the E> i flow line diameter, the return _D2 wire diameter, V _is the flow line insulation of the intended thickness, V ₂ designed thickness and designed for the thermal conductivity of the X _No sealant return line insulation of with the help of 43 calculate the theoretical heat loss per unit length of the conduit using the formula:

Rö, e, <

(t _e - tt) + o, v, e (tv ^- tt), (3) where R0, _e , e is the theoretical heat resistance between the flow medium and the ground surface, and R0, _v , e is ^the return heat transfer medium, and the theoretical thermal resistance between the soil surface.

Rö, e, e ⁼ Rsz, e, e Rcsl + Rcs + Rt where R _{sz> e} , _{e is} the theoretical resistance of the heat insulation of the flow pipe,

R _cs [thermal resistance of convection heat transfer in the air of the concrete duct,

R _{cs is} ^the thermal resistance of ^the concrete channel wall,

Rt is the soil heat resistance and

R6, v, e ~ R5, v, ed Rcsl 3 Rcs T Rf, (4) where R is _{SZ; v} , e is ^the theoretical thermal resistance of ^the return line insulation.

We then compare the actual and theoretical heat losses. If q / q _e > 1, the thermal insulation of the wires is deduced from the value. The q / q _e ratio65 from the table developed by us

-2184 i 56 the thermal insulation capacity (consistency) factor of the insulation can be determined. On the other hand, the q / q _e ratio can be used to calculate the actual heat loss of power line systems over any period of time.

Heat loss can be accurately calculated by approximating a series of constant states. Formula 3 can be used to calculate the theoretical heat loss of the system for any given day. The sum of these gives the theoretical heat loss for any period of the system (eg, year).

The theoretical heat loss in terms of q / q _{e can be used to} determine the actual heat loss of the system.

Claims (1)

A method for determining the effective heat loss (q) and thermal resistance (R _sz ) of a pipeline length in the case of operational overhead lines laid in a concrete duct, characterized in that the geometric centerline 20 of the concrete duct suitable mid digestion are taken at least 10 cm long, solid, soil 25 consistency of retained soil sample from the concrete channel fedlapjától and directly beneath the earth's surface, and the concrete channel earth covering the center, which determine the thermal conductivity coefficient, (X _t) determining> and arithmetic mean training the mean thermal conductivity coefficient (X _t ), and after sampling, drilling a hole between the sampling points to the top of the concrete conduit for the district heating line 30, a depth gauge (H) and then a thermometer suitable for measuring the temperature of the concrete gutter cover (t _w ) in contact with the concrete duct cover, preferably adapted for temperature transducing; then - continuously, continuously, or at least hourly, record the temperature of the concrete duct cover (t _w ), the surface temperature (tt) of the conduit and the '40 other heat sources and the closest consumer to the conduit or heat generator flow medium temperature (t _e ) and return medium temperature (t _v ), then arithmetic averaging gives the average concrete channel cover temperature (t _w ), the average flow water temperature (te), the average return water temperature (t _v ) and average soil surface temperature (F _t ), then determine the soil resistance (R _t ) using the average soil thermal conductivity (λ {) and calculate the actual heat loss per unit length of the district heating pipe ( (q) using the formula below: Q ~ (hv - tf), then the conduit design characteristics of the supply pipe diameter (Dj), the return line diameter (D _2), the flow line thermal insulation thickness (V), the return line thermal insulation thickness (V ₂₎ and Calculating the theoretical thermal resistance (R _{SZi e} , e) and the thermal insulation (R ^ _v _ _e ) of the return pipe, using the known formula, to determine the thermal conductivity of the pipes (X _sz ). theoretical heat resistance (R _{sz> Cj e} ) _? furthermore, by means of the known formulas, the theoretical heat resistance (R _{SZ; Vj e} ) and the ground heat resistance (R _t ) of the return line insulation, determine the theoretical heat resistance (Rg, _e , e) between the flow medium and the ground surface, and a theoretical thermal resistance between the surface (ro, _{V, ε),} then calculating the value of the theoretical heat loss (Q _e) of the formula: Qe ~ ro, e, e (fe ^- tt) h ro, v, e (TV ^- 1 _t ) and then comparing the theoretical heat loss (q _e ) and the actual heat loss (q) and, if q / q _e > 1, from that to the loss of the thermal insulation of the wires and to the thermal resistance of the heat insulation of the feed pipe (R _{n> e} ) and / or a decrease in the thermal resistance (R _s , v) of the return line insulation.