HXR500

The purpose of HXR500 is to desuperheat the argon we receive from the customer and cool it to as close to its condensation temperature as possible. The cooling comes from N2 vapor that comes out of HXR 600.

HXR500 calculations and equations

• Calculate the thermal duty change for the argon in HXR500 when it cools.
  • hxr500_duty_ar = argon mass flow rate * argon heat capacity * argon temperature change in HXR_500
  • argon mass flow rate: coldbox_lbh
  • gaseous argon heat capacity = (1.248E+02 + (- 4.672E-03*T) + (3.471E-05*T^2) + (2.306E-07*T^3) + (- 8.318E-10*T^4) + (-7.554E-12*T^5))/1000
  • argon temperature change = TE601 - TE501
• Assume there is an equal amount of energy that has been removed from the argon that has been used to heat the nitrogen in HXR500 and conduct a duty balance to calculate the flow rate of nitrogen through HXR500.
  • hxr500_n2_mfr_balanced = hxr500_duty_ar/(gaseous nitrogen heat capacity * nitrogen temperature change in HXR_500)
  • gaseous nitrogen heat capacity = (249.73 + (- 0.0148*T) + (0.0002*T^2) + (9E-07*T^3) + (- 7E-09*T^4) + (-4E-11*T^5))/1000
  • nitrogen temperature change = TE504 - saturation temperature of N2
  • saturation temperature of N2 = -333.55 + (0.9963*PT_603) + (-0.0058*PT_603^2)
• Use temperature measurements from the thermocouples surrounding HXR500 to calculate the log mean temperature difference; this represents the average temperature difference between the N2 and argon streams.
  • LMTD = (TE_501 - TE_504 - TE_601 - Tsat N2)/(log(TE_501 - TE_504/TE_601 - Tsat N2))
• Compute the heat transfer coefficient in HXR500. This represents how well the HXR is transferring heat
  • HXR_500_HTC = hxr500_duty_ar/LMTD * Heat Transfer Area; Heat Transfer Area is pulled from a table and is different for each site.
• During a heat, the fouling resistance in the HXR is calculated. This is done by comparing the reciprocal of the heat transfer coefficient during that heat to the reciprocal of the heat transfer coefficient when the HXR was clean
  • hxr500_fr = (1/hxr500_htc) - (1/hxr500_htc_clean)
  • hxr500_htc_clean is described in more detail below. It is calculated as a function of flow rate
• Calculate the fouling Biot number, this is an alternative metric for reviewing the extent of fouling and gives a % output that represents how much % of the HXRs original heat transfer capacity is being wasted due to fouling.
  • hxr500_biot = hxr500_htc_clean * hxr500_fr

take a look at github

Output metrics:

• hxr500_duty_ar
• hxr500_n2_mfr_balanced
• hxr500_n2_mfr_balanced_scfm
• hxr500_lmtd
• hxr500_htc
• hxr500_fr
• hxr500_biot
• hxr500_ar_boil_t
• hxr500_n2_ar_flow_ratio
• hxr500_htc_clean
• hxr500_output_efficiency = 100 * hxr500_htc / hxr500_htc_clean

Inputs alteration

1. Input flow is: ft_202_scfm if coldbox_scfm > 100
2. te601 = ....:
   • ARS15002: TE601 - 20
   • ARS13007: TE601 - 34
   • other: TE601

Heat Transfer Area Values

List of HXR500 Areas for each site provided below.

Site	Site #	Surface Area (ft2)
Cartech	13007	-
ATI2	15008	-
OER 2	16006	3207.65
HMI	14002	4596.19
ATI3	16005	796.529
WG	15002	699.7
ATI1	20009	-
SMC	19004	-

hxr500_htc_clean

Our heat exchangers when they were purchased had a baseline efficiency value that determines how well they transfer heat. That is this metric the clean heat transfer coefficient.

As the heat exchanger operates for a long time it slowly becomes dirty and becomes less efficient, which we track by the live heat transfer coefficient. HX500_htc.

We use the clean value here to compare it to the live value to see how efficiency is dropping over time.

The energy a heat exchanger can output is dependent on the rate or argon flowing through it, as obviously if you want to cool more argon, you need to pull more energy per second from the stream. This is why this metric the clean HTC, has a correlation with flow rate.

Default Formula:

• Polynomial fitting based on ft_202_scfm
• for ARS19004: FT501 * 0.000774 + 0.2928 github
• for ARS14002: 0.0036 * coldbox_scfm + 0.55 github

Site specific behavior

site	formula
ARS15002	0.0036 * lb_per_hour_to_scfm(arFlowRate) + 0.55
ARS19004	FT_501 * 0.000774 + 0.2928