HXR600

The purpose of HXR 600 is to condense the cooled argon that comes out of HXR500. Because it is not quite at its condensation temperature, the argon is normally cooled around 30-50F in HXR600 before it is condensed. Cooling is done by liquid nitrogen, which vaporizes in the exchanger and is heated to slightly above its boiling temperature (it is superheated).

There are some key differences in calculating the heat transfer coefficient for HXR 600. This is because the flow of argon from HXR500 is not the only argon being cooled in HXR600. There is also an additional amount of flow from TK700 that is sending any argon recycling within the system back into HXR600.

When we try and perform a duty balance on the liquid nitrogen flow entering HXR 600 with the argon flow coming from HXR500 alone, we find there is more duty going into the nitrogen. This is because the argon recycle flow rate has not been accounted for. By performing a duty balance we can therefore estimate the amount of argon recycling from TK700. The steps for the analysis of HXR600 are therefore:

• Calculate the thermal duty change for the argon in HXR600 when it is heated and condenses
  • hxr600_ar_duty = argon mass flow rate * argon enthalpy of condensation
  • argon enthalpy of condensation = 163.6294416 * 0.429923
  • argon mass flow rate: coldbox_lbh
• Calculate the thermal duty change for the nitrogen in HXR600 when it is heated an vaporizes *hxr600_n2_duty = N2 mass flow rate * N2 enthalpy of evaporation
  • nitrogen enthalpy of evaporation = 198.9285714 * 0.429923
  • Nitrogen mass flow rate = hxr500_n2_mfr_balanced
• Calculate the mass flow rate of argon flowing through HXR600 that would provide enough heat to vaporize the nitrogen in the previous step
  • argon max mass flow rate = hxr500_duty_N2/argon enthalpy of condensation
• Calculate the difference between the mass flow rate of argon flowing through HXR600 in the previous step and the amount of argon entering HXR600 from HXR500. This gives the TK700 argon recycle mass flow rate.
  • hxr600_ar_recycle_mfr = argon max mass flow rate - argon mass flow rate
• Estimate the amount of nitrogen being used to condense the argon being recycled from TK700
  • hxr600_n2_recycle_mfr = hxr600_ar_recycle_mfr * (N2 mass flow rate/argon mass flow rate)
• Use pressure readings from PT601 and PT603 to calculate the temperatures of liquid nitrogen and liquid argon.
  • saturation temperature of N2 = -333.55 + (0.9963* PT603) + (-0.0058* PT603^2)
  • saturation temperature of argon = -322.82 + (1.5963* PT601) + (-0.0157* PT601^2)
• Calculate the temperature difference between the liquid nitrogen and liquid argon
  • Temperature difference = saturation temperature of N2 - saturation temperature of argon
• Calculate the heat transfer coefficient in HXR600
  • hxr600_htc = hxr600_ar_duty/(Temperature difference * Heat Transfer Area)
  • Heat Transfer Area is pulled from a table and is different for each site.
• Calculate the fouling resistance in the HXR at the time of measurement
  • hxr600_fr = (1/hxr600_htc) - (1/hxr600_htc_clean)
  • hxr600_htc_clean is described in more detail below. It is calculated as a function of flow rate
• Calculate the fouling Biot number in the HXR at the time of measurement
  • hxr600_biot = hxr600_htc_clean * hxr600_fr

take a look at github

Output metrics:

• hxr600_ar_duty
• hxr600_n2_duty
• hxr600_ar_recycle_q
• hxr600_ar_recycle_mfr
• hxr600_ar_recycle_scfm
• hxr600_n2_recycle_mfr
• hxr600_n2_recycle_scfm
• hxr600_htc
• hxr600_fr
• hxr600_biot
• hxr600_htc_clean

Input conditions:

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 HXR600 Areas for each site provided below.

Site	Site #	Surface Area (ft2)
Cartech	13007	2658.5
ATI2	15008	2218.9
OER 2	16006	3544.7
HMI	14002	5003.1
ATI3	16005	unknown
WG	15002	1707
ATI1	20009	-
SMC	19004	-

hxr600_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. HX600_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