The units must be consistent in the following equation: delta T = Q/(Cp * mass) = (internal energy * EQHEAT * FWORK)/(Cp * mass) Q = heat Cp = specific heat capacity (same as HC in *mat_thermal) EQHEAT is a conversion factor. heat = internal energy * EQHEAT. See http://ftp.lstc.com/anonymous/outgoing/support/heat_units.pdf for a discussion of units in coupled thermal-structural analyses (Shapiro 2005). Also http://ftp.lstc.com/anonymous/outgoing/support/FAQ_docs/heat_transfer_class.pdf (Pdf pages 102-104 (Chapter 8, pages 8-3 to 8-8)). For a glossary of heat transfer terms, see http://www.efunda.com/formulae/heat_transfer/home/glossary.cfm http://www.physchem.co.za/Heat/Heat.htm#Units For conversion factors, see http://www.gordonengland.co.uk/conversion/coeftt.htm http://www.gordonengland.co.uk/conversion/energy.htm _____________________________________________________ Possible over simplification?... The EQHEAT value is directly dependent on the units of specific heat capacity HC. If HC is input in consistent units of energy/(mass * temperature) = length^2/(time^2 * temperature), then EQHEAT = 1.0. If HC is input in units that contain BTU or calories, that's a sure sign that EQHEAT should not be 1.0. Heat capacity (sometimes loosely called specific heat) is in units of energy/(mass*temperature). So in English units, this is (lbf*inch)/((lbf*sec^2/inch)*degrees) = (inch^2)/(sec^2*degrees) http://www.engineeringtoolbox.com/specific-heat-capacity-d_339.html says 1 Btu/lbm F = 4186.8 J/kg K = 1 kcal/kg C We can expand that to show that 1 Btu/lbm F = 4186.8 J/kg K = 1 kcal/kg C = 6.4881e6 in^2/(sec^2 K) = 3.6045e6 in^2/(sec^2 F) Some pertinent unit conversions: Force: lbf * 4.448 = N Mass: snails * 175.08 = kg where a snail is lbf*sec^2/inch Length: inch * 1/39.37 = m Energy: lbf*inch * 4.448/39.37 = joule (or N*m) From http://www.engineersedge.com/materials/specific_heat_capacity_of_metals_13259.htm , Specific Heat Capacity Conversions: 1 Btu/(lb-°F) = 4186.8 J/(kg-K) 1 Btu/(lb-°F) = 4.1868 J/(g-°C) 1 Btu/(lb-°F) = 1.8 Btu/(lb-°C) _________________________________________________________________________ Heat capacity Cp has units of N * m/(kg * degC) = m^2/(sec^2 * degC) = m^2/(sec^2 * degC) Transform heat capacity from mks to English, multiply by: 0.22482 lbf/N * 39.37 inch/m * 175.08 kg/(lbf-s^2/inch) * 5/9 degC/degF or (39.37 inch/m)^2 * 5/9 degC/degF = 861. Transform heat capacity from tonnes,mm,sec,N to English, multiply by: = 861E-6 ___________________________________________________ RE: steel Ticket#2017040510000228 The value of HC different for ton-mm-sec and kg-m-sec HC's unit is J/kg/c = N*m/kg/c = (kg*m/s^2)*m/kg/c = m^2/sec/c = (1000mm)^2/sec/c so for ton-mm-sec 460 m^2/sec/c = 460*10^6 mm^/sec/c for kg-m-sec HC is 460 for ton-mm-sec HC is 4.6*10^8 for English, HC is 460 * 861 = 3.96e5 John Zhao _______________________________________________________________________ On subject of terminology in LS-DYNA Manual (heat capacity vs. specific heat): On 2/4/2013, Jim wrote: Thermodynamics vs. Heat Transfer. Enough said. Art Shapiro wrote: > Now make sure you tell all the users (GM, FORD, Mercedes, Toyota, Honda, > etc.) that nothing has changed and they can use the same value they > have been using. Tell them they do not have to multiply the value by > the standard state value of water like specific gravity. Be clear on > this because they are going to call support. > > There will always be problems with jargon in different subject areas. > Thermodynamics uses "specific" to designate per unit mass. Heat transfer > uses "specific" to reference a water standard. > > The answer is "use J/kg C" which ignores the jargon. > > Art > > Jim Day wrote: >> Hi, Art. >> >> I'll revisit the *airbag changes I made and add the units expected for >> Cv and Cp (stated generically as energy/(mass*degree)) so as to avoid >> misinterpretation. Furthermore, unless you tell me it's a bad idea, >> I'm inclined to change "heat capacity" to "specific heat" in >> describing Cv and Cp. >> >> I'm well aware that anything wikipedia or any online source says must >> be taken with a grain of salt, but for better or worse, Joe Blow >> engineer sometimes makes use of this information if it's a subject >> somewhat outside of his field. One thing that one could conclude >> from the online sources is that specific heat is a less ambigous term >> than heat capacity. Just as an example, here's what wikipedia >> (http://en.wikipedia.org/wiki/Heat_capacity) says ... >> *"Heat capacity* (usually denoted by a capital /C/, often with >> subscripts), or *thermal capacity*, is the measurable >> physical quantity >> that shows the amount >> of heat required to change the >> temperature of a substance >> by a given amount. In the International System of Units >> (SI), >> heat capacity is expressed in units of joule(s) (J) >> per kelvin (K) >> . >> >> Derived quantities that specify heat capacity as an intensive property >> , i.e., independent >> of the size of a sample, are the *molar heat capacity*, which is the >> heat capacity per mole >> of a pure substance, and the *specific heat capacity*, often simply >> called *specific heat*, which is the heat capacity per unit mass of a >> material." >> >> >> As you suggested, I'll leave *mat_thermal alone. To my knowledge, no >> customer has questioned the meaning of HC in *mat_thermal. >> >> >> Thanks, >> Jim >> >> Art Shapiro wrote: >>> A 2nd thought that would make this all clear, not only for Cp but for >>> all other quantities in the user manual, would be to include example >>> units in SI. Such as for density [kg/m**3], Cp [J/kg C], etc. >>> >>> Jargon, such as specific, is confusing. >>> >>> Art >>> >>> Art Shapiro wrote: >>> >>>> I suggest leaving things alone. >>>> >>>> Historically "specific" meant comparison to water. Specific heat is >>>> defined as the ratio of the heat capacity of a substance to the heat >>>> capacity of an equal quantity of water. Water being an accepted >>>> standard. This made sense in the 1800's. But we now know properties are >>>> a function of pressure and temperature so water is not a very good >>>> standard. This is like specific gravity. >>>> >>>> I have never seen heat capacity used without mass in the denominator. >>>> Try to find a reference book that gives values for heat capacity in >>>> units of energy/degree. Since it has been called "heat capacity" for >>>> MAT_THERMAL in this manual and preceding manuals since 1982 with no >>>> confusion, I see no reason to change it. >>>> >>>> Art >>>> >>>> Jim Day wrote: >>>> >>>>> Hi, Art. >>>>> >>>>> In response to bug #8187, I changed the description "heat capacity" in >>>>> *airbag_simple_airbag_model and *airbag_wang_nefske to "specific heat >>>>> capacity" to hopefully make it clear that the units are energy per >>>>> degree per unit mass. Heat capacity is just energy (or heat) per >>>>> degree, is it not? >>>>> >>>>> Related to this matter, I notice all the *mat_thermal descriptions in >>>>> the Manual refer to HC as "heat capacity" rather than "specific heat >>>>> capacity". Should that be changed? >>>>> >>>>> Thanks, >>>>> Jim >>>>>