CN103868627A - Pressure-type heat meter - Google Patents

Abstract

The invention discloses a pressure-type heat meter. The inventions aims to provide a heat meter simple in structure, easy in manufacturing techniques, low in cost, high in precision, uneasy to clog, and small in maintenance amount. The heat meter comprises a calculator, an incoming water temperature sensor, an outgoing water temperature sensor, and a flow sensor. The incoming water temperature sensor and the outgoing water temperature sensor are connected to an incoming water temperature sensor input terminal and an outgoing water temperature sensor input terminal of the calculator respectively. The flow sensor comprises a throttling means, an upstream pressure sensor and a downstream pressure sensor. The upstream pressure sensor is directly installed on an upstream pipe wall pressure measuring port of the throttling means, and the downstream pressure sensor is directly installed on a downstream pipe wall pressure measuring port of the throttling means. Electrical signal output terminals of the upstream pressure sensor and the downstream pressure sensor are connected to an upstream pressure sensor input terminal and a downstream pressure sensor input terminal of the calculator respectively.

Description

Pressure type calorimeter

Technical field

The present invention relates to a kind of measuring apparatus, particularly a kind of thermal gauge.

Background technology

At present, what the calorimeter that China's heat metering is used adopted substantially has two types, and one is mechanical heat meter, and one is ultrasonic calorimeter.Mechanical heat meter flow measurement part is rotary vane meter, due to its complicated in mechanical structure, often occurs latch up phenomenon, has also proved this point in practice process.The flow measurement principle of ultrasonic calorimeter mostly adopts the time difference method of the poor method of ultrasonic propagation velocity.There is following problem in ultrasound wave time difference method in actual applications:

1, the impact of sound time delay

Ultrasonic flow meter measurement of fluid flow key be the measurement of time, but in the time of practical application, the following current time T measuring ₁with adverse current time T ₂comprise sound time delay a1, a2 that circuit, cable, transducer and sound wedge etc. produce, therefore must have been measured and deduct.But, want to record accurately also not a duck soup of a1, a2, because in the time carrying out time measurement, supply voltage must be stablized, otherwise the time delay of components and parts also can change to some extent in circuit, in battery powered situation, must carry out at set intervals the measurement of a1, an a2.Sound time delay a1, a2 increase with flow again, and flow more large deviation is also larger.

2, utilize the measurement of ultrasound wave fluid flow, its difficulty is mainly: the flow rate of liquid of generally measuring is below every number of seconds rice, and the velocity of sound in liquid is about 1500m/s, and the variable quantity that flow rate of liquid brings the velocity of sound is only 10 at the most ^-3the order of magnitude, in the metering of fluid flow, in the time that measurement flow rate of liquid precision prescribed reaches 1%, it is 10 that the measuring accuracy of the velocity of sound is required ^-5to 10 ^-6, it is very difficult wanting to keep such high precision for a long time.

3, the uneven distribution of liquid flow field

The flow rate of liquid that ultrasonic flow meter records is actually along the line average velocity V on transonic path ₁, the flow that record liquid should be the face mean flow rate V along cross-section of pipeline ₂.And actual conditions be liquid in pipeline flow not be to be uniformly distributed along cross-section of pipeline diameter flow velocity, by the line average velocity V recording ₁calculating face average velocity V ₂time must carry out the correction of velocity flow profile coefficient, this coefficient is the function of fluid Reynolds number.But fluid exists significantly sudden change at the interval adjusted coefficient K from laminar flow to turbulent transition, and this shows that to instrument value effect is larger, and with certain randomness, be difficult to the Reynolds number of accurate Fluid Computation to carry out just right correction.So in the time that flow velocity is lower, flow measurement precision is difficult to improve.

4, the ultrasonic flow meter based on adopting propagation speed differential method is not suitable for the measurement of the liquid that contains granule foreign or bubble in liquid, bubble can produce 5 times of above errors of measured value, if gas in pipelines is too much, can makes ultrasound wave generation scattering and instrument can not be worked.

5, ultrasonic transducer is one of device of most critical, has the technical indicator of a series of harshnesses

Temperature is very large on the impact of ultrasonic transducer, therefore, most important to the compensation of temperature coefficient, especially near lower-capacity point, sometimes can cause the even measuring error of hundreds of times of decades of times, the circuit of particularly measuring with time difference method.Transducer is also very sensitive to pressure, and variation in water pressure is very large for measuring accuracy impact, and the pressure reduction between present building high level and low layer is very large, also needs to revise according to the working curve under transducer pressure-bearing.

6, easily stop up

At present, the flowmeter that adopts ultrasound wave time difference method is to place two reflecting optics in flowmeter matrix central authorities substantially, see into that from flowmeter matrix water intake end face sizable area is reflected eyeglass and support member blocks, because heat supply hot water is containing incrustation scale and impurity, so ultrasonic calorimeter is also easily blocked.On catoptron, fouling also can make measuring accuracy reduce in addition.

Summary of the invention

The present invention has overcome the shortcoming of prior art, provides that a kind of accuracy of measuring is high, manufacture and easy to use, low cost, anticlogging calorimeter.

The invention provides a kind of pressure type calorimeter for reaching described object, comprise: counter, inflow temperature sensor, leaving water temperature sensor, flow sensor, described inflow temperature sensor and leaving water temperature sensor are connected to the input end of inflow temperature sensor and the input end of leaving water temperature sensor of counter, and described flow sensor comprises restriction device, upstream pressure sensor and downstream pressure sensor, and this flow sensor does not arrange differential pressure gauge and connecting pipe; Described upstream pressure sensor is directly installed on the upstream wall pressure tapping of restriction device, downstream pressure sensor is directly installed on the downstream wall pressure tapping of restriction device, and the output terminal of the electrical signal of upstream pressure sensor and the electric signal of downstream pressure sensor is connected to the input end of upstream pressure sensor and the input end of downstream pressure sensor of counter.

The restriction device of the flow sensor of pressure type calorimeter of the present invention can adopt wedge shape restriction device.

The upstream pressure sensor of the flow sensor of pressure type calorimeter of the present invention and downstream pressure sensor can adopt MEMS pressure transducer.

Pressure type calorimeter of the present invention designs according to the city-building industry standard CJ128-2007 of the People's Republic of China (PRC), and the theory of heat metering is the hot measuring principle of enthalpy potential method, and its basic calculating formula is:

$\mathrm{Qi}={\∫}_{\mathrm{\τ}0}^{\mathrm{\τ}1}\mathrm{\ρ}\×q_V\×\mathrm{\Δh}\×\mathrm{d\τ}---\left(1\right)$

In formula:

The heat that Qi---system discharges or absorbs, the J of unit;

Q _v---the volumetric flow rate of the calorimeter of flowing through, unit is m ³/ h:

ρ---the density of the water of the calorimeter of flowing through, unit is kg/m ³;

Δ h---under heat-exchange system import and outlet temperature, the enthalpy of water is poor, and unit is J/kg;

τ---the time, unit is h.

The principle of measuring flow of the present invention is: in the pipeline that is full of liquid, circulation area of fixed placement is less than the long-pending throttling element of pipeline section, and in pipeline, a fluid stream will cause local contraction when by this throttling element.In contraction place, flow velocity increases, and according to the Bernoulli equation incompressible fluid of law of conservation of energy, in flow process, flow velocity increase must cause static pressure to reduce.Therefore, before and after throttling element, certain pressure differential will be produced.Can push away to obtain the volumetric flow rate formula of incompressible fluid according to Bernoulli equation and continuity equation:

$q_V=\frac{C}{\sqrt{1-{\mathrm{\β}}^4}}\·\frac{\mathrm{\π}}{4}\·d^2\·\sqrt{\frac{2(p_1-p_2)}{\mathrm{\ρ}}}---\left(2\right)$

In formula:

Q _v---the volumetric flow rate of the flow sensor fluid of flowing through, unit is m ³/ s;

C---efflux coefficient;

D---throttling element opening diameter, unit is m;

The ratio of β---throttling element opening diameter d and the interior diameter D of upstream measuring tube;

ρ---the fluid density under the temperature and pressure while measuring volumetric flow rate, unit is kg/m ³;

P ₁---the static pressure at wall pressure tapping place, flow sensor upstream, unit is Pa;

P ₂---the static pressure at wall pressure tapping place, flow sensor downstream, unit is Pa.

Known according to formula (2), the volumetric flow rate q of ducted liquid _vwith the poor (P of static pressure before and after throttling element ₁-P ₂) square root be directly proportional.Therefore, as long as measure respectively the static pressure P before throttling element ₁with the downstream static pressure P after throttling element ₂and the density p of liquid just can calculate ducted fluid flow.

The flow sensor of pressure type calorimeter of the present invention is that a kind of modified differential pressure flow sensor is pressure type flow quantity sensor, and this flow sensor is not directly to measure restriction device upstream and downstream liquid differential pressure, but measures restriction device upstream and downstream hydrostatic pressure; So flow sensor of the present invention does not arrange differential pressure gauge and connecting pipe, and a wall pressure tapping is respectively set on the fore-and-aft survey pipe of restriction device, each static pressure P that a direct measuring flow sensor of high sensitivity pressure transducer is installed on two wall pressure tappings ₁with downstream static pressure P ₂, then by P ₁, P ₂and the density p of hot water at the temperature that records of temperature sensor is brought in formula (2) and is tried to achieve volumetric flow rate q _v.

The water pressure sensor that the present invention adopts is high-precision MEMS micro-electromechanical pressure transducer.

Compared with prior art, the invention has the beneficial effects as follows:

1,, owing to adopting the MEMS micro-electromechanical pressure transducer of high precision, highly sensitive advanced technology, improved the measuring accuracy of calorimeter for rill calorimetric metering;

2, simple for structure, manufacturing process is simple;

3,, compared with ultrasonic calorimeter, can significantly reduce costs;

4, be difficult for stopping up;

5, working stability is reliable, and maintenance is very little.

Brief description of the drawings

Fig. 1 is pressure type calorimeter embodiment wedge shape pressure type calorimeter structural representation of the present invention;

Fig. 2 is wedge shape restriction device axial section;

Fig. 3 is wedge shape restriction device water (flow) direction view.

The arc opening 206 of the counter 101 inflow temperature sensor 102 leaving water temperature sensor 103 flow sensor 104 restriction device 105 upstream pressure sensor 106 downstream pressure sensor 107 wedge shape throttling element 201 upstream wall pressure tapping 202 downstream wall pressure tapping rear measuring tube 205 wedge shape restriction device of 203 before measurement buret 204 in figure

Embodiment

Below in conjunction with accompanying drawing and embodiment, the present invention is described in further detail:

Referring to Fig. 1, Fig. 1 is pressure type calorimeter embodiment wedge shape pressure type calorimeter structural representation of the present invention.

The embodiment of the present invention is wedge shape pressure type calorimeter, comprising: counter 101, inflow temperature sensor 102, leaving water temperature sensor 103, wedge flow sensor, upstream pressure sensor 106, downstream pressure sensor 107 and LCD display.

Refer to Fig. 2 and Fig. 3, Fig. 2 is wedge shape restriction device axial section, and Fig. 3 is wedge shape restriction device water (flow) direction view.Wedge flow sensor is made up of wedge shape restriction device, upstream pressure sensor 106 and downstream pressure sensor 107, and wedge shape restriction device is made up of wedge shape throttling element 201, upstream wall pressure tapping 202, downstream wall pressure tapping 203, before measurement buret 204 and rear measuring tube 205.

The main structure of wedge flow sensor is that wedge shape throttling element 201 is for being designed to the wedge shape part of V-type, by wedge shape throttling element 201 top down when mounted, be conducive to like this pass through smoothly the arc opening 206 of wedge shape restriction device containing liquid or the thick liquid of suspended particle, for the liquid that has suspended particle, the pipe that level is installed, suspension tends to be deposited on the first half of pipe, if measure this liquid with other flowmeter, suspension tends to be deposited on the upstream side of throttling element and stops up.And the best angle design of wedge shape throttling element 201 can be eliminated stagnant area and makes containing the liquid of suspended particle smoothly by wedge shape throttling element.So wedge flow sensor is highly suitable for the measurement of high viscosity, impure and suspended particle fluid flow.

In the time that fluid to be measured is flowed through wedge flow sensor, cause liquid local contraction by wedge shape throttling element 201, thereby the flow velocity of liquid increases, static pressure reduces.Measure the static pressure P of wedge shape flow sensor ₁with downstream static pressure P ₂, then by P ₁, P ₂and the density p of hot water at the temperature that records of temperature sensor is brought the volumetric flow rate q that tries to achieve liquid in formula (3) into _v.

The volumetric flow rate of wedge flow sensor is calculated formula:

$q_V=\frac{C}{\sqrt{1-m^2}}\·m\·\frac{\mathrm{\π}}{4}\·D^2\·\sqrt{\frac{2(p_1-p_2)}{\mathrm{\ρ}}}---\left(3\right)$

In formula:

Q _v---flow through the volumetric flow rate of wedge flow sensor, unit is m ³/ s;

C---efflux coefficient;

D---the interior diameter of upstream measuring tube, unit is m;

M---orifice size ratio is the arc circulation area ratio long-pending with cross-section of pipeline;

ρ---the density of water under temperature and pressure when measurement volumes flow, unit is kg/m ³;

P ₁---flow sensor static pressure, unit is Pa;

P ₂---flow sensor downstream static pressure, unit is Pa.

The course of work of embodiment of the present invention wedge shape pressure type calorimeter is as follows:

1, per interval τ counter 101 reads lower column data:

(1), read the upstream heat hydrostatic pressure P that the upstream pressure sensor 106 of wedge flow sensor records ₁, and be stored in storage;

(2), read the downstream heat hydrostatic pressure P that the downstream pressure sensor 107 of wedge flow sensor records ₂, and be stored in storage;

(3), read the inflow temperature t that inflow temperature sensor 102 detects ₁, and be stored in storer;

(4), read out the leaving water temperature t that water temperature sensor 103 detects ₂, and be stored in storer;

2, according to the inflow temperature t recording ₁try to achieve the density p into water;

3, by ρ, P ₁with P ₂substitution formula (3), calculates volumetric flow rate q _v;

4, according to inflow temperature t ₁try to achieve the enthalpy h into water ₁;

5, according to leaving water temperature t ₂try to achieve the enthalpy h of water outlet ₂;

6, calculate the poor Δ h=h of enthalpy ₁-h ₂;

7, by q _v, in Δ h, ρ and time τ substitution formula (1), calculate calorie value Qi;

8, Qi is deposited in total amount of heat totalizer Q.

The course of work of described wedge shape pressure type calorimeter is the water inlet that hypothesis wedge shape pressure type calorimeter is arranged on heat-exchange system above.

The pressure transducer of embodiment of the present invention application is the pressure transducer that adopts MEMS technology to manufacture, this MEMS (Micro Electromechanical System, being microelectromechanical systems) pressure transducer can be by the designing technique of similar integrated circuit and manufacturing process, carry out high precision, produce in enormous quantities cheaply, make pressure survey and control become simple, easy-to-use and intelligent.

Current MEMS pressure transducer has silicon piezoresistance type pressure sensor and Silicon Pressure Sensor of Capacitance, the micromechanics electronic sensor both generating on silicon chip.

Silicon piezoresistance type pressure sensor is to adopt high-accuracy semiconductor resistor foil gauge composition resistance bridge to convert metering circuit as power electricity, it is high that MEMS pressure transducer has output sensitivity, stable performance, in batches reliability, reproducible, the advantages such as lower power consumption and extremely low cost.

MEMS silicon piezoresistance type pressure sensor adopts the fixing circular stress cup silicon thin film inwall of periphery, adopt MEMS technology directly four high-accuracy semiconductor gauges to be engraved on to its surface stress maximum, composition Hui Sidun measuring bridge, as power electricity conversion metering circuit, this physical quantity of pressure is directly converted to electric weight, and its measuring accuracy can reach 0.03%FS.MEMS pressure transducer is the new high-tech product recently growing up.

The major advantage of embodiment of the present invention wedge shape pressure type calorimeter is as follows:

1, hot measuring accuracy is high;

2, Reynolds number usable range is wide, and applicable to extremely low Reynolds number (ReD=300), and the Reynolds number upper limit can reach 10 ⁶above;

3, there is automatic cleaning action, without delay, non-maintaining;

4, simple for structure, manufacture simple, easily adjustment, low pressure loss, resistance to wear, easy to install;

5, can move reliably and with long-term low cost;

6, wedge shape pressure type calorimeter is front without filtrator is installed;

7, can also be used for the measurement of solid-liquid two-phase and gas-liquid two-phase fluid, this advantage is that ultrasonic calorimeter is incomparable;

8, wedge flow sensor of the present invention through demarcate separately have higher measuring accuracy can reach ± 0.5%, also can reach ± 3% left and right of not proven wedge flow sensor measurement precision; Repeatable accuracy can reach ± and 0.2%;

9, wedge flow sensor of the present invention has abnormal anticlogging function, be applicable to measure mud, coal tar, pitch, coal aqueous suspensions and other high viscosity fluid, so wedge shape pressure type calorimeter of the present invention is can be not blocked in the time measuring the heat supply hot water that contains incrustation scale and impurity.

Claims (3)

1. a pressure type calorimeter, comprise: counter (101), inflow temperature sensor (102), leaving water temperature sensor (103), flow sensor (104), described inflow temperature sensor (102) and leaving water temperature sensor (103) are connected to the input end of inflow temperature sensor and the input end of leaving water temperature sensor of counter (101), it is characterized in that: described flow sensor (104) comprises restriction device (105), upstream pressure sensor (106) and downstream pressure sensor (107), this flow sensor (104) does not arrange differential pressure gauge and connecting pipe, described upstream pressure sensor (106) is directly installed on the upstream wall pressure tapping of restriction device (105), downstream pressure sensor (107) is directly installed on the downstream wall pressure tapping of restriction device (105), and the output terminal of the electric signal of the electrical signal of upstream pressure sensor (106) and downstream pressure sensor (107) is connected to the input end of upstream pressure sensor and the input end of downstream pressure sensor of counter (101).

2. pressure type calorimeter according to claim 1, is characterized in that: the restriction device of described flow sensor (104) is wedge shape restriction device.

3. pressure type calorimeter according to claim 1, is characterized in that: the upstream pressure sensor (106) of described flow sensor (104) and downstream pressure sensor (107) are MEMS pressure transducer.

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