Quasiadiabetic differential scanning calorimeter

Patent metadata

Field	Value
Publication number	US-9857241-B2
Application number	US-201314425473-A
Country	US
Kind code	B2
Filing date	Aug 30, 2013
Priority date	Sep 4, 2012
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A method of operating a differential scanning calorimeter wherein errors in the heat flow rate measurement are reduced by operating the calorimeter in a quasiadiabatic mode and by employing a heat flow rate measurement algorithm that includes the leakage heat flow rate. The temperature of the DSC enclosure is controlled independently of the temperature of the measuring system, which allows the temperature difference between the sample and reference containers and the enclosure to be minimized, thus minimizing leakage heat flow.

First claim

What is claimed is:

1. A method of measuring a differential heat flow in a differential scanning calorimeter, wherein the differential scanning calorimeter comprises a block of high thermal conductivity material within an enclosure, said block of high thermal conductivity material comprising a sample measuring system and a reference measuring system, said method comprising:
measuring a temperature of the enclosure;
controlling the temperature of the block of high thermal conductivity material according to a predetermined temperature program;
measuring T 0 , ΔT, ΔT 0 , and T e , where T 0 is the temperature of the block of high thermal conductivity material, ΔT is the difference between the temperature of the sample measuring system and the temperature of the reference measuring system, ΔT 0 is the difference between the temperature of the block of high thermal conductivity material and the temperature of the sample measuring system, and T e is the temperature of the enclosure;
calculating a temperature of a sample container in the sample measuring system and a temperature of a reference container in the reference measuring system based upon the measured values of T 0 , ΔT and ΔT 0 ;
controlling the temperature of the enclosure to follow a weighted average of the calculated temperature of the sample container and the calculated temperature of the reference container to minimize heat leakage between the sample and reference measuring systems and the enclosure; and
calculating a differential heat flow to the sample container with respect to a heat flow to the reference container based upon measuring ΔT, ΔT 0 , T a and T e by using an algorithm that comprises corrections to the measured heat flow to the sample container based in part upon the difference between the temperature of the enclosure and the temperature of the sample container.

2. The method of claim 1 , wherein the step of calculating a differential heat flow to the sample container with respect to the reference container comprises using one of the following equation and any other algebraically equivalent equations to the following equation:

q
=

q
s

⁡

(

1
+

R
ss

R
se

)

+

T
e

-

T
s

R
se

-

m
ps

m
pr

⁢

T
.

ss

T
.

rr

⁢

(

q
r

⁡

(

1
+

R
rr

R
re

)

+

T
e

-

T
s

+

Δ
⁢

⁢
T

R
re

)

where:
q is the differential heat flow rate to the sample container with respect to the heat flow to the reference container;
q s is the measured sample heat flow rate;
q r is the measured reference heat flow rate;
R ss is the thermal contact resistance between the sample container and its calorimeter;
R rr is the thermal contact resistance between the reference container and its calorimeter;
R se is the thermal resistance between the sample container and the enclosure;
R re is the thermal resistance between the reference container and the enclosure;
T e is the temperature of the enclosure;
T s is the temperature of the sample measuring system;
m ps is the mass of the sample container;
m pr is the mass of the reference container;
{dot over (T)} ss is the sample container heating rate;
{dot over (T)} rr is the reference container heating rate; and
ΔT is equal to T s −T r , where T r is the temperature of the reference measuring system.

3. The method of claim 1 , further comprising calibrating the differential scanning calorimeter by conducting a first constant heating rate experiment with empty containers and a second constant heating rate experiment at the same constant heating rate as in the first experiment with a sample of known heat capacity in the sample container and a similar sample of known thermal conductivity in the reference container.

4. The method of claim 1 , wherein the differential scanning calorimeter comprises a base structure comprising a first flange and a second flange, further comprising thermal resistors in the form of slender cylindrical rods joining the first flange to the second flange.

5. The method of claim 1 , wherein the weighted average uses a weighting factor which is greater than or equal to zero and less than or equal to 1.

6. The method of claim 1 , wherein the weighted average of the calculated temperature of the sample container and the calculated temperature of the reference container is a straight averag

Assignees

• Waters Technologies Corp

Inventors

• Danley Robert L

Classifications

• G01N25/20

  by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity (calorimeters per se G01K) · CPC title

• G01K17/08 Primary

  based upon measurement of temperature difference {or of a temperature} · CPC title

• G01N25/4833 Primary

  specially adapted for temperature scanning · CPC title