Method for rapidly measuring specific heat in calibration stage based on heat flow type calorimeter

Abstract

The invention belongs to the field of chemical thermodynamics. The invention discloses a method for rapidly measuring specific heat in a calibration stage based on a heat flow type calorimeter. According to the measurement method, a new calibration operation mode of the heat flow type calorimeter is designed, and the specific heat is efficiently measured in combination with an algorithm. According to the method, the determination of the specific heat can be completed through single calibration measurement, and a convenient and effective method is provided for obtaining the specific heat of a substance by combining with an experimental process of measuring reaction heat by a heat flow type calorimeter.

Description

Technical Field

[0001] The present invention belongs to the field of chemical engineering thermodynamics. Specifically, it relates to a method for measuring the constant-pressure specific heat of a substance. Background Art

[0002] As basic physical property data, the constant-pressure specific heat of a substance is commonly used to determine the energy required for heat absorption or removal during the heating and cooling processes of the substance.

[0003] The main methods for measuring the specific heat of a substance include differential scanning calorimetry, mixing method, and electrothermal method. Under the condition of ensuring a certain sample amount and accuracy, this method provides a new operation method for measuring the specific heat. Summary of the Invention

[0004] The present invention provides a new method for measuring the specific heat of a substance. This method measures the heating and cooling curves during the calibration stage of a heat flux calorimeter to achieve the measurement of the specific heat of the substance.

[0005] The present invention provides the operation process for the specific heat measurement, and the specific process is as follows:

[0006] First, weigh an appropriate amount of the sample to be measured, and record its mass as m. Add it to the heat flux calorimeter and control the temperature to the target temperature at which the specific heat needs to be tested.

[0007] Record the temperature of the sample to be measured in the heat flux calorimeter at this time, denoted as T r,0 , and record the temperature of the jacket of the heat flux calorimeter at this time, denoted as T j,0 .

[0008] Adjust the temperature control mode of the heat flux calorimeter to the T j temperature control mode, turn on the calibration heater, and heat the sample to be measured at a constant power for a period of time.

[0009] After the temperature of the sample to be measured has risen significantly, turn off the calibration heater and adjust the temperature control mode of the heat flux calorimeter to the T r temperature control mode.

[0010] After controlling the temperature until the temperature of the sample to be measured is stable again, end the measurement process.

[0011] The present invention provides the data calculation method for the specific heat measurement, and the calculation method process is as follows:

[0012] The heat flux calorimeter will record the real-time temperature of the sample to be measured, denoted as T r (t), the real-time jacket temperature, denoted as T j (t), and the real-time calibration power q c (t). Record the highest temperature of the sample to be measured during the operation process as T r,max , and the lowest temperature of the sample to be measured as T r,min, the temperature of the sample to be measured at the end point of the operation process is T r,end , the jacket temperature at the end point of the operation process is T j,end .

[0013] Calculate the energy flowing in for calibration heating, and the calculation formula is Qc(t)=∫q c (t)dt.

[0014] Calculate the total heat transfer coefficient of the heat flux calorimeter during the operation process, and the calculation formula is UA = Q c,end / (∫(T r (t)-T j (t)-(T r,0 -T j,0 +T r,end -T j,end ) / 2)dt).

[0015] Calculate the heat transfer curve of the heat flux calorimeter Qr(t)=∫(T r (t)-T j (t)-(T r,0 -T j,0 +T r,end -T j,end ) / 2)dt.

[0016] Calculate the cumulative heat curve, and its calculation formula is Q accu (t)=Qc(t)-Qr(t). Denote the maximum value of Q accu , the minimum value of Q accu , and the value of Q accu at the end point of the operation process as Q accu,max , Q accu,min , Q accu,end .

[0017] The specific heat of the sample to be measured is C p =((Q accu,max -0) / (T r,max -T r,0 )+(Q accu,end -Q accu,min ) / (T r,end -T r,min )) / (2×m). Specific implementation cases

[0018] The following further elaborates on the present invention in combination with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0019] Implementation case:

[0020] At room temperature of 24.3°C, 290 g of the standard sample was added to the heat flow calorimeter, and the temperature was controlled at 25.0°C. The sample temperature and the jacket temperature of the heat flow calorimeter were recorded at this time. The temperature control mode of the heat flow calorimeter was adjusted to T j temperature control mode, the calibration heater was turned on, and the sample to be tested was heated at a power of 5 W for a period of time. After 15 min, the calibration heater was turned off, and at the same time, the temperature control mode of the heat flow calorimeter was adjusted to T r temperature control mode. After temperature control for 15 min, the temperature of the sample to be tested was stable again, and the measurement process was ended. Data calculation was carried out according to the data calculation method for specific heat measurement described above.

[0021] At 25.0°C, the specific heat of the standard sample was 4.18, and the specific heat of the standard sample obtained by testing through the steps of the present invention was 4.178, with a small error.

Claims

1. A method for rapidly determining specific heat during the calibration phase of a heat flux calorimeter, characterized in that: A new calibration operation mode for heat flux calorimeter was designed, combined with an algorithm to achieve efficient determination of specific heat.

2. The method according to claim 1, characterized in that The method is applicable to the determination of the constant-pressure specific heat capacity of liquid, solid or slurry substances.

3. The new calibration operation mode according to claim 1, characterized in that: The temperature control mode of the heat flux calorimeter in the front part of the calibration process is T j Temperature control mode: The temperature control mode of the heat flux calorimeter in the latter part of the calibration process is T r Temperature control mode.

4. The algorithm according to claim 1, characterized in that The calculation of the overall heat transfer coefficient UA is based on the integration of the average temperature difference during the calibration period.

5. The algorithm according to claim 1, characterized in that The specific heat is calculated by calculating the cumulative heat.