CN101876617B - Method for improving accuracy of hydrogen storage performance measurement by constant volume method - Google Patents

Abstract

The invention relates to a method for reducing the measurement error in the process of testing the hydrogen storage performance of hydrogen storage materials by a constant volume testing system. Under the condition of not changing a system structure, the method comprises the following steps of: segmenting a sample chamber volume according to the characteristics of temperature distribution of a test system; and calculating the amount of gases in the sample chamber. In the method, the system measurement error caused by a great temperature difference between a sample temperature and the room temperature is reduced, and the measurement accuracy of the test system is improved.

Description

A kind of method that improves accuracy of hydrogen storage performance measurement by constant volume method

Technical field

The invention belongs to a kind of reciprocity appearance method test macro in measuring hydrogen storage material hydrogen storage capability process, according to test macro Temperature Distribution characteristics, the amount of gas in the sample chamber is carried out volume and temperature section respectively to be calculated, reduce measuring error, and then raising hydrogen storage material hydrogen storage capability measuring accuracy, the method for objective evaluation hydrogen storage material hydrogen storage property.

Background technology

Measure appearance method and gravimetric methods such as the most general method of material hydrogen storage capability has.Simple, convenient, flexible etc. appearance method proving installation, therefore obtained using widely.Its ultimate principle is in the closed system of constant volume, measure the hydrogen storage material sample and inhale the variation of (putting) hydrogen front and back system pressure, adopt equation of state of real gas to calculate the closed system of constant volume, the variable quantity of gas before and after absorption of hydrogen storage material sample or desorption hydrogen and obtain hydrogen storage material and store hydrogen capacity.Accompanying drawing 1 such as is at an appearance method test system structure synoptic diagram.As shown in Figure 1, vacuum valve V1, hydrogen valve V2 and helium valve V3 are installed respectively on vacuum-pumping tube, hydrogen draft tube and the helium draft tube, and vacuum-pumping tube, hydrogen draft tube and helium draft tube are respectively by air inlet total valve V4 and receive on the system pipeline; Pressure accumulating chamber 1 and sample chamber 2 are attempted by on the opposite side of system pipeline, sample valve V5 are installed, setting pressure sensor P on the system pipeline between air inlet total valve V4 and the sample valve V5 on the system pipeline between pressure accumulating chamber 1 and the sample chamber 2.Before sample valve V5 opened, hydrogen pressure was P in the pressure accumulating chamber 1 _Sys, temperature is T _Sys, hydrogen pressure is P in the sample chamber 2 _Sam, temperature is T _SamAfter sample valve V5 opened, system pressure was P after hydrogen storage material suction (putting) hydrogen balance _Eq, the suction of hydrogen storage material (putting) hydrogen mole capacity n[H2 then] calculate by following formula and to obtain:

N[H2]=n (P _Sys, V _Sys, T _Sys)+n (P _Sam, V _Sam, T _Sam)-(n (P _Eq, V _Sys, T _Sys)+n (P _Eq, B _Sam, T _Sam)) n in (1) formula (T) function numerical value adopts the BWR equation of gas state to calculate to obtain for P, V:

$P=\mathrm{RT}\frac{n}{V}+({\mathrm{<figure-callout\; id="0"\; label="B"\; filenames="H2009102418336E00021.png,H2009102418336E00022.png"\; state="\{\{state\}\}">B</figure-callout>}}_0\mathrm{RT}-A_0-\frac{C_0}{T^2}){\left(\frac{n}{V}\right)}^2+(\mathrm{bRT}-a){\left(\frac{n}{V}\right)}^3+\mathrm{a\&alpha;}{\left(\frac{n}{V}\right)}^6+\frac{\mathrm{<figure-callout\; id="2"\; label="c\; T"\; filenames="H2009102418336E00011.png,H2009102418336E00012.png"\; state="\{\{state\}\}">c</figure-callout>}}{T^{}}\&times;{\left(\frac{n}{V}\right)}^3\&times;\left[(1+\mathrm{\&gamma;}{\left(\frac{n}{V}\right)}^2)\exp (-\mathrm{\&gamma;}{\left(\frac{n}{V}\right)}^2)\right]---\left(2\right)$

Wherein: pressure P units MPa, temperature T are K, volume V unit/ml, R=8.3144JmolK ^-1, other parameters are as follows:

Table 1H ₂Gas BWR state equation parameter

In the formula (1), V _SysFor the cumulative volume of connecting tube volume between pressure accumulating chamber's 1 volume and pressure accumulating chamber 1 and the sample valve V5, in order to reduce the influence of temperature fluctuation to system pressure, V _SysUsually remain on constant temperature T _SysV _SamCumulative volume for connecting tube volume between sample chamber 2 volumes that take up hydrogen storage material and sample chamber 2 and the sample valve V5.With T _SysThe temperature difference, sample chamber 2 temperature T _SamCan be as required, for a certain constant temperature of liquid nitrogen temperature in several Baidu high temperature range, to satisfy the hydrogen storage material testing requirement.Generally, be the temperature T that sample chamber 2 is placed testing requirement _Sam, and the connecting tube between sample chamber 2 and the sample valve V5 is to place under the room temperature environment.Obviously, cumulative volume V _SamThe sample chamber be not all really to be in T _SamTemperature, wherein, connecting tube between sample chamber 2 and the sample valve V5 but be in room temperature environment, and be left in the basket usually in the process of this problem gas flow in the actual computation sample chamber.Between sample chamber 2 and sample valve V5 the connecting tube volume much smaller than the sample chamber one of 2 volume more than the order of magnitude, perhaps sample chamber 1 temperature T _SamWhen being more or less the same, adopt the method for gas flow in formula (1) the calculation sample chamber, can not produce bigger experimental error, otherwise produce significant measuring error hydrogen storage material hydrogen storage capability test result with room temperature.

Summary of the invention

The purpose of this invention is to provide a kind of method that appearance method test macro hydrogen storage capability measuring accuracy such as improves.According to test macro Temperature Distribution characteristics, the sample chamber cumulative volume is carried out staging treating, the amount of gas in the sample chamber is carried out the segmentation of volume and temperature respectively and calculate, reduce systematic measurement error, and then improve hydrogen storage material hydrogen storage capability measuring accuracy.

For achieving the above object, the present invention takes following technical scheme:

A kind of method that appearance method test macro precision such as improves, these structures of holding the method test macros are: hydrogen draft tube, helium draft tube and vacuum-pumping tube are respectively by the air inlet total valve and receive on the system pipeline; Pressure accumulating chamber and sample chamber are attempted by on the opposite side of system pipeline, sample valve and pressure transducer are installed on the system pipeline between pressure accumulating chamber and the sample chamber, it is characterized in that, the sample chamber cumulative volume is carried out two sections staging treating, promptly be divided into the volume of sample chamber itself and sample valve volume to the system pipeline of sample chamber.

A kind of method that improves appearance method test system and test hydrogen storage material hydrogen storage capability precision such as using, the hydrogen storage capability of appearance method test system and test hydrogen storage materials such as employing, it is characterized in that, calculating suction (putting) the hydrogen mole capacity n[H2 of hydrogen storage material] time adopt below formula:

n[H2]＝n(P _sys，V _sys，T _sys)+n(P _sam，V _sam1，T _sam)+n(P _sam，V _sam2，T _sam2)-(n(P _eq，V _sys，T _sys)+n(P _eq，V _sam1，T _sam)+n(P _eq，V _sam2，T _sam2))

Wherein: n[H2] be the suction of hydrogen storage material (putting) hydrogen mole capacity;

P _SysBe pressure in the pressure accumulating chamber before the sample valve open;

V _SysVolume for (back) pressure accumulating chamber before the sample valve open; The volume of this pressure accumulating chamber is constant before the sample valve open or behind the sample valve open, therefore, and V _SysVolume for pressure accumulating chamber;

T _SysTemperature for the pressure accumulating chamber of (back) before the sample valve open; The temperature of this pressure accumulating chamber is constant before the sample valve open or behind the sample valve open, therefore, and T _SysTemperature for pressure accumulating chamber;

P _SamPressure for the sample chamber before the sample valve open;

V _Sam1Volume (removing the shared spatial volume of hydrogen storage material sample) for (back) sample chamber itself before the sample valve open; The volume of this sample chamber itself is constant before the sample valve open or behind the sample valve open, therefore, and V _Sam1Volume (removing the shared spatial volume of hydrogen storage material sample) for sample chamber itself;

T _SamTemperature for (back) sample chamber itself before the sample valve open; The temperature of this sample chamber itself is constant before the sample valve open or behind the sample valve open, therefore, and T _SamTemperature for sample chamber itself;

V _Sam2For (back) before the sample valve open connects the system pipeline volume of sample valve to sample chamber itself; System pipeline volume own is constant to this connection sample valve to the sample chamber before the sample valve open or behind the sample valve open, therefore, and V _Sam2For connecting the system pipeline volume of sample valve to sample chamber itself;

T _Sys2For sample valve open (back) connects the system pipeline temperature of sample valve to sample chamber itself; System pipeline temperature own is constant to this connection sample valve to the sample chamber before the sample valve open or behind the sample valve open, therefore, and T _Sys2For connecting the system pipeline temperature of sample valve to sample chamber itself;

P _EqFor pressure accumulating chamber, sample chamber itself behind the sample valve open be connected the pressure of sample valve to the system pipeline in sample chamber own.

Advantage of the present invention: do not changing under the system structure design prerequisite, according to test macro Temperature Distribution characteristics, the sample chamber volume segments is handled the amount of gas in the calculation sample chamber, and then improve hydrogen storage material hydrogen storage capability etc. and hold the method measuring accuracy, satisfy hydrogen storage material and accurately measure demand.

Description of drawings

Appearance method test macro synoptic diagram such as Fig. 1

Appearance method test macro sample chamber volume segments such as Fig. 2 are divided synoptic diagram

Fig. 3 Li-Mg-N-H material 503K transfers the hydrogen curve

Isothermal is inhaled the hydrogen curve under Fig. 4 absorbent charcoal material 77K

Embodiment

To cumulative volume V in sample chamber in the test macro _SamCarry out volume and temperature section and divide processing, as shown in Figure 2.With the actual temperature T that is in _SamIn sample chamber 2 volume markings be V _Sam1, sample valve V5 is V to the connecting tube volume markings between the sample chamber 2 _Sam2(V _Sam2=V _Sam-V _Sam1), connecting tube temperature of living in is T _Sam2, T generally _Sam2Be approximately equal to ambient temperature.V _Sam1And V _Sam2Though the volume size is different with temperature, residing pressure size is identical.Corresponding two parts volume is quoted the amount that different volumes and temperature are carried out gas in the segmentation calculation sample chamber respectively, and then is obtained the hydrogen storage material hydrogen storage capability, and formula is as follows:

n[H2]＝n(P _sys，V _sys，T _sys)+n(P _sam，V _sam1，T _sam)+n(P _sam，V _sam2，T _sam2)

(3)

-(n(P _eq，V _sys，T _sys)+n(P _eq，V _sam1，T _sam)+n(P _eq，V _sam2，T _sam2))

The present invention is further illustrated and explanation to adopt instantiation below, but the present invention is not limited in present embodiment.

Embodiment 1:

The 1 volume V of pressure accumulating chamber in the test macro _Sys=38ml (T _Sys=300K), sample valve V5 is to connecting tube volume V between the sample chamber 2 _Sam2=5.2ml.Pack in the sample chamber 2 Li-Mg-N-H hydrogen storage material of 1g, temperature T in sample chamber 2 _Sam=300K adopts the helium calibration sample chamber cumulative volume V of 0.1-0.5MPa down _Sam=18ml, then sample chamber 2 volume V _Sam1=V _Sam-V _Sam2=18-5.2=12.8ml.Adopt sample chamber cumulative volume V _SamWhether segmentation to be, the amount of gas in the calculation sample chamber and obtaining under the 503K, and Li-Mg-N-H material hydrogen storage capability is with pressure history result (T as shown in Figure 3 _Sam=503K, T _Sam2=300K).Adopt sample chamber V _SamIn the amount segmentation of gas to calculate and obtain Li-Mg-N-H material hydrogen storage capability under 503K, 9.6MPa be 4.95wt%, measured value is near the theoretical hydrogen storage capability of Li-Mg-N-H material 5.5wt%, under the same terms, sample chamber V _SamIn gas amount not segmentation to calculate and obtain Li-Mg-N-H material hydrogen storage capability under 503K, 9.6MPa be 6.43wt%, be higher than the theoretical hydrogen storage capability of Li-Mg-N-H material, do not conform to the actual conditions.

Embodiment 2:

Pressure accumulating chamber's volume V in the test macro _Sys=41ml (T _Sys=300K), sample valve V5 is to connecting tube volume V between the sample chamber 2 _Sam2=5.6ml.The 2g absorbent charcoal material of packing in the sample chamber 2, temperature T in sample chamber 2 _Sam=300K adopts the helium calibration sample chamber cumulative volume V of 0.1-0.5MPa down _Sam=8.4ml, then sample chamber 2 volume V _Sam1=V _Sam-V _Sam2=8.4-5.6=2.8ml.Adopt sample chamber cumulative volume V _SamWhether segmentation, the amount of gas in the calculation sample chamber and obtain under the 77K absorbent charcoal material hydrogen storage capability with the pressure history result as shown in Figure 4.Adopt sample chamber V _SamThe amount segmentation of middle gas is calculated and obtained absorbent charcoal material hydrogen storage capability under 77K, 8.0MPa is 1.86wt%, under the same terms, and sample chamber V _SamIn gas amount not segmentation calculate and obtain absorbent charcoal material hydrogen storage capability under 77K, 8.0MPa and be-4wt%, it is negative that hydrogen storage capability shows, and do not conform to the actual conditions.

Claims (2)

1. method that appearance method test system and test hydrogen storage material hydrogen storage capability precision such as improves, these structures of holding the method test macros are: hydrogen draft tube, helium draft tube and vacuum-pumping tube are respectively by the air inlet total valve and receive on the system pipeline; Pressure accumulating chamber and sample chamber are attempted by on the opposite side of system pipeline, sample valve and pressure transducer are installed on the system pipeline between pressure accumulating chamber and the sample chamber, it is characterized in that, the sample chamber cumulative volume is carried out two sections staging treating, promptly be divided into the volume of sample chamber itself and sample valve volume to the system pipeline of sample chamber.

2. method that improves appearance method test system and test hydrogen storage material hydrogen storage capability precision such as using, the hydrogen storage capability of appearance method test system and test hydrogen storage materials such as employing is characterized in that, at suction (putting) the hydrogen mole capacity n[H that calculates hydrogen storage material ₂] time adopt below formula:

n[H ₂]＝n(P _sys，V _sys，T _sys)+n(P _sam，V _sam1，T _sam)+n(P _sam，V _sam2，T _sam2)

-(n(P _eq，V _sys，T _sys)+n(P _eq，V _sam1，T _sam)+n(P _eq，V _sam2，T _sam2))

Wherein: n (T) function numerical value adopts the BWR equation of gas state to calculate acquisition for P, V:

$P=\mathrm{RT}\frac{n}{V}+(B_0\mathrm{RT}-A_0-\frac{C_0}{T^2}){\left(\frac{n}{V}\right)}^2+(\mathrm{bRT}-a){\left(\frac{n}{V}\right)}^3+\mathrm{a\&alpha;}{\left(\frac{n}{V}\right)}^6+\frac{c}{T^2}\&times;{\left(\frac{n}{V}\right)}^3\&times;\left[(1+\mathrm{\&gamma;}{\left(\frac{n}{V}\right)}^2)\exp (-\mathrm{\&gamma;}{\left(\frac{n}{V}\right)}^2)\right]$

N[H ₂] be the suction of hydrogen storage material (putting) hydrogen mole capacity;

P _SysBe pressure in the pressure accumulating chamber before the sample valve open;

V _SysVolume for (back) pressure accumulating chamber before the sample valve open;

T _SysTemperature for the pressure accumulating chamber of (back) before the sample valve open;

P _SamPressure for the sample chamber before the sample valve open;

V _Sam1Volume (removing the shared spatial volume of hydrogen storage material sample) for (back) sample chamber itself before the sample valve open;

T _SamTemperature for (back) sample chamber itself before the sample valve open;

V _Sam2For (back) before the sample valve open connects the system pipeline volume of sample valve to sample chamber itself;

T _Sam2For sample valve open (back) connects the system pipeline temperature of sample valve to sample chamber itself;

P _EqFor pressure accumulating chamber, sample chamber itself behind the sample valve open be connected the pressure of sample valve to the system pipeline in sample chamber own.

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