10 - Thermal properties

Question 1

specific heat capacity c_p

definition

Answer 1

characterize the capability of a material to store heat

J /(kg*K)

Question 2

specific heat capacity c_p

formula

Answer 2

c_p = Q / (m*dT)

Q = heat input (J)
m = mass (kg)
dT = resulting temperature difference

Question 3

specific heat capacity of rocks

c_p,rock

Answer 3

c_p,rock = sum( xi * Vi * c_p,i )

Question 4

specific heat capacity of rocks

difference between sedimentary and igneous rocks

Answer 4

sedimentary has higher values than igneous rocks

because of pore water (high c_p ~4kJ/kgK)

Question 5

specific heat capacity of rocks

correlation c_p & T

Answer 5

c_p increase with increasing T

not linear

Question 6

Heat flow density q

Answer 6

qi = lambda_ij * (dT/dxj)

material specific

in Watt

Question 7

Thermal conductivity

lambda

Answer 7

property of material to conduct heat (temperature dependend)

lambda_ij -> i & j refer to directions

in W / (mK) or mkg / (s^3*K)

Question 8

Thermal diffusivity a

definition

Answer 8

penetration and temperature changes into a material

in m^2/s

Question 9

Thermal diffusivity a

formula

Answer 9

aij = lambda_ij / c_p * rho

Question 10

physical processes of heat transfer (3)

Answer 10

conduction

convection

radiation

Question 11

conduction

Answer 11

heat passes through the substance of the body

itself

Question 12

convection

Answer 12

heat is transferred by relative motion of

portions of the heated body

Question 13

radiation

Answer 13

heat is transferred direct between distant portions

of the body by electromagnetic radiation

Question 14

advection

Answer 14

movement of some material by flowing water (e.g. dissolved cations)

Question 15

measurements of thermal conductivity

Answer 15

1. Steady state method
2. Transient method
3. Optical scanning technique

Question 16

measurement of thermal conductivity

1. Steady state method

Answer 16

slide 5

cylindrical sample between two cylinders of reference material

one ref. cylinder end heated

after steady state is reached,
T drop within rock compared with drop in ref. cylinder
–> thermal conducticity

Question 17

measurement of thermal conductivity

1. Steady state method

qi

Answer 17

qi= lamba_ij * (dT/dxj)

with

lambda = qL / ( A(T1-T2) )

q = C * dT * m / t

Question 18

measurement of thermal conductivity

2. Transient method

Answer 18

Temperature as function of time

line source (needle probe) with heater & temp. sensor in sample

Transient hot wire method

slide 6