CN102052293A - Confirming method of lift needed by cooling circulating water system - Google Patents

Abstract

The invention discloses a confirming method of the lift needed by a cooling circulating water system. The method comprises the following steps of: confirming a current operating lift H of a water pump according to a Bernoulli equation; then, substituting a static lift h of the water pump into an equation: H=h+kQ2 to calculate a resistance coefficient k of a pipe network; and finally, substituting a flow rate Q1 practically needed by the known heat exchanger into an equation: h1=h+kQ12 to acquire a water pump lift H1 practically needed by the system. In the invention, the confirming method of the lift needed by the cooling circulating water system can exploit the energy-saving potentiality of a water system to the greatest extent and improve the energy utilization rate of the water system.

Description

Definite method of the required lift of cooling circulating water system

Technical field

The invention belongs to the cooling circulating water field, relate to the industry that iron and steel, chemical industry, electric power, metallurgy etc. are used cooling circulating water, specifically is definite method of the required lift of a kind of cooling circulating water system.

Background technique

The rapid expansion of the efficiency demand that causes along with the develop rapidly of Chinese national economy and extensive growth pattern, energy resource supply seriously lags behind the growth rate of energy consumption, gives China's sustainable economic development, building a conservation-minded society has constituted great threat.Wherein water pump accounts for about 25% of total electricity consumption, to realizing energy-saving and cost-reducing target important influence.

Cooling circulating water system is made up of motor, water pump, valve, heat-exchanger rig, cooling tower and pipeline and pipeline fittings etc., the liquid of needs being lowered the temperature by heat-exchanger rig carries out exchange heat, then by cooling tower cooling, a recycling repeatedly again cover system.In industries such as petrochemical industry, electric power, iron and steel, metallurgy, the power consumption of cooling circulating water system accounts for the 20-30% of business electrical total amount.

When cooling circulating water system designed, it was calculating by theory that lift is established a capital really, and adds safety coefficient, when actual motion, water pump flow bigger than normal was moved, and was in fall-back state; Perhaps make water pump be in the operation of efficient district, but also increased the lift loss at valve place simultaneously by closing valve regulation.

Country carries forward vigorously low-carbon economy now, the energy-conservation industry of water system is also risen thereupon, at the too high problem of water system rated lift, adopting various means to reduce pump head, thereby reach purpose of energy saving, is according to manometric reading but the actual required lift of water system is established a capital really, directly calculate by Bernoulli's equation, its result of calculation is often than the required lift height of reality, and is therefore, energy-conservation not thorough.

Summary of the invention

At the defective that above-mentioned prior art exists, the present invention aims to provide definite method of the required lift of a kind of cooling circulating water system, can excavate the energy-saving potential of water system to greatest extent, improves the capacity usage ratio of water system.

The technological scheme that the present invention takes is that definite method of the required lift of a kind of cooling circulating water system is characterized in that, comprises the steps:

(1) terminal valve on the pipeline in the cooling circulating water system is all opened;

(2) measure the water pump inlet and outlet pressure, and then calculate water pump inlet outlet pressure differential Δ P;

(3) determine the water pump lift H of operation now according to Bernoulli's equation

$H=\mathrm{\ΔZ}+\frac{\mathrm{\ΔP}}{\mathrm{\ρg}}+\frac{{V_2}^2-{V_1}^2}{2g}+\mathrm{\Δh}$

The discrepancy in elevation (m) that Δ Z wherein---water pump is imported and exported

The pressure reduction (KPa) that Δ P---water pump is imported and exported

V ₂---the outlet velocity (m/s) of water pump,

V ₁---the inlet velocity (m/s) of water pump, owing to calculate the pressure head of the water inlet pool water surface, so V ₁=0

Drag losses (m) between Δ h---water pump is imported and exported;

ρ---fluid density (kg/m ³)

G---gravity accleration (m ²/ s)

(4) go out water pump with flowmeter survey and now move flow Q;

(5) according to the water inlet and outlet water-head, determine the vertical water potential difference of the water inlet and outlet of cooling circulating water system,

Be the static lift h of water pump;

(6) according to formula H=h+kQ ²Calculate the resistance of pipe system coefficient k;

The lift of H---water pump

The static lift of h---water pump, i.e. the discrepancy in elevation of pipeline import and export

The flow of Q---water pump

K---resistance of pipe system coefficient

(7) bring the actual required flow Q1 of known heat-exchanger rig into formula H1=h+kQ1 ², wherein the static lift h of water pump, resistance of pipe system coefficient k are constant, the actual required pump head H1 of the system that calculates.

Because the lift during system design is often greater than the required lift of reality, water pump can move by flow bigger than normal during actual motion, thereby cause actual motion flow Q much larger than the actual required flow Q1 of heat-exchanger rig, and the lift H that calculates according to Bernoulli's equation is also greater than the required lift H1 of reality.Therefore, by above-mentioned definite method,, make that the actual required lift H1 that calculates at last is more accurate, thereby reach energy-conserving action in conjunction with the actual required flow Q1 of heat-exchanger rig.

In sum, definite method of the required lift of cooling circulating water system of the present invention can be excavated the energy-saving potential of water system to greatest extent, improves the capacity usage ratio of water system.

Description of drawings

Fig. 1 is the schematic representation of cooling circulating water system;

In the accompanying drawings,

1-pond, 2-cooling tower, 3-gate valve, 4-water pump, 5-pressure gauge, 6-safety check, 7-butterfly valve, 8-filter screen, 9-water-thermometer, 10-heat-exchanger rig

Embodiment

Embodiment one:

As shown in Figure 1, the cooling circulating water system that provides of present embodiment is made up of pond 1, cooling tower 2, gate valve 3, water pump 4, pressure gauge 5, safety check 6, butterfly valve 7, filter screen 8, water-thermometer 9, heat-exchanger rig 10 and pipeline and pipeline fittings etc.Blacking indicates expression in the water pump group among the figure is just at the water pump of running state.

The basic condition of above-mentioned cooling circulating water system is as follows:

1, pump (1#) that model is 8SH-9 of on-the-spot operation, and annual 24 hour operation; The relevant parameter of this pump is as described below,

Rated flow: 280m ³/ h rated head: 63m rotating speed: 2950r/min;

The motor model that adopts: Y280S-2 rated power: 75kW voltage rating/electric current: 380V/140A power factor: 0.86 rotating speed: 2970r/min;

System's import water level is about 1.5m, and the water outlet height is 35.5m

Open the valve on the pipeline in all cooling circulating water systems, comprise the water pump terminal valve.

2, operating mode and time:

Operating mode: move one, a usefulness two is equipped with;

Working time: annual 24 hour operation, calculated by 8760 hours working time.

3, system operational parameters

The on-the-spot operating conditions investigation of raw water pump before table 1 technological transformation

4, running situation analysis before the technological transformation

4.1 the water pump operation lift calculates:

With table 1 data is foundation, calculates pump head (getting into the water water surface and pump discharge pressure table place two section calculating pump actual motion lifts) according to Bernoulli's equation.

$H=\mathrm{\ΔZ}+\frac{\mathrm{\ΔP}}{\mathrm{\ρg}}+\frac{{V_2}^2-{V_1}^2}{2g}+\mathrm{\Δh}$

The discrepancy in elevation (m) the Δ Z that Δ Z wherein---water pump is imported and exported

Δ Z=h1 (pumping the oral thermometer height)-h2 (pump intake water level in water pool)=1m-1.5m=-0.5

Pressure reduction (Pa) the Δ P=385.3Kpa that Δ P wherein---water pump is imported and exported

Δ P=P1 (pump discharge downstream pressure)-P0 (import basal plane water level pressure head)=400KPa-14.7KPa=385.3KPa

Import basal plane water level pressure head P0=1.5/102KPa=14.7KPa wherein

V wherein ₂---the outlet velocity V of water pump ₂=0.697 (m/s)

V wherein ₁---the inlet velocity V of water pump ₁=0 (m/s)

Drag losses (m) Δ h=0.5m between Δ h wherein---water pump is imported and exported

According to Bernoulli's equation, the pressure head that the water inlet pool of calculating water pump goes out to the exit of pump pressure gauge, this promptly is the lift of water pump.

To go up the table data brings this formula into and calculates: the lift H=39.3m of water pump

According to formula H=h+kQ ²Calculate the resistance of pipe system coefficient k;

h＝35.5m-1.5m＝34m

$k=\frac{H-h}{Q^2}=\frac{39.3-34}{330*330}=0.0000487$

Wherein: H---the lift of water pump

The static lift of h---system, promptly pipeline is imported and exported the discrepancy in elevation of two liquid levels

The flow of Q---water pump, field instrument test gained

Nameplate parameter according to heat-exchanger rig draws the actual required flow Q1 of heat-exchanger rig parameter, carries it into above-mentioned formula, and h, k are constant, the actual required pump head H1 of the system that calculates;

According to the on-site actual situations requirement, pump duty is got Q1=280m3/h after the technological transformation

H1＝h+kQ ₁ ²＝34+0.0000487×(280) ²＝37.82m

Therefore, by above-mentioned definite method, having drawn the actual required lift of pump is H1=37.82m.

By the foregoing description as can be known, the required lift of water system that draws with conventional method is 39.3 meters, should be 37.82 meters and can calculate the actual required lift of water system accurately with our rule, thereby lift can be reduced to 37.82 meters when transforming, eliminate unnecessary energy loss, better reached energy saving purposes.

Claims (1)

1. definite method of the required lift of cooling circulating water system is characterized in that, comprises the steps:

(1) terminal valve on the pipeline in the cooling circulating water system is all opened;

(2) measure the inlet and outlet pressure of water pump in the cooling circulating water system, and then calculate water pump inlet outlet pressure differential Δ P;

(3) determine the water pump lift H of operation now according to Bernoulli's equation

$H=\mathrm{\ΔZ}+\frac{\mathrm{\ΔP}}{\mathrm{\ρg}}+\frac{{V_2}^2-{V_1}^2}{2g}+\mathrm{\Δh}$

The discrepancy in elevation (m) that Δ Z wherein---water pump is imported and exported

The pressure reduction (KPa) that Δ P---water pump is imported and exported

V ₂---the outlet velocity (m/s) of water pump,

V ₁---the inlet velocity (m/s) of water pump, owing to calculate the pressure head of the water inlet pool water surface, so V ₁=0

Drag losses (m) between Δ h---water pump is imported and exported;

ρ---fluid density (kg/m ³)

G---gravity accleration (m ²/ s)

(4) go out water pump with flowmeter survey and now move flow Q;

(5) according to the water inlet and outlet water-head, determine the vertical water potential difference of the water inlet and outlet of cooling circulating water system,

Be the static lift h of water pump;

(6) according to formula H=h+kQ ²Calculate the resistance of pipe system coefficient k;

The lift of H---water pump

The static lift of h---water pump, i.e. the discrepancy in elevation of pipeline import and export

The flow of Q---water pump

K---resistance of pipe system coefficient

(7) bring the actual required flow Q1 of known heat-exchanger rig into formula H1=h+kQ1 ², wherein the static lift h of water pump, resistance of pipe system coefficient k are constant, the actual required pump head H1 of the system that calculates.

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