Thermal management of catalytic converter with heat pipe embedded in thermal energy storage to reduce cold start emissions

ABSTRACT

The Thermal Energy Storage (TES) System aids in improving the cold start efficiency of the catalytic converter (CC). To further improve the TES and CC performance, loop heat pipes embedded into the PCM, TES unit are presented. For evaluation, three cases are considered: Case 1; CC without TES, Case 2; CC with TES, Case 3; CC with a heat pipe embedded in PCM TES. Mg₇₀Zn_24.9Al_5.1 is used as PCM and paraffin oil as the working fluid for the heat pipe. Three 30 minute transient cycles with idle events in between were run, with the engine soaking for 30 minutes at ambient conditions with varied loads (0 to 100%) at 2000 rpm. Heat storage and release cycles were run for each load condition. Average warm-up HC, NO_x and CO conversion efficiency improvement of 45–85% with Case 3, 35–62% with Case 2 compared to Case 1 were observed. Heat storage time was observed to be lower by ~ 35% for Case 3 while the heat retention time was observed to be better for Case 2 by ~44%. System efficiency and effectiveness were found to be better up to 14% and ~0.2 with Case 3 compared to Case 2. Overall Case 3 showed better performance with some penalty on the heat retention time compared Case 2.

KEYWORDS:

• Heat pipe
• catalytic converter
• conversion efficiency
• thermal energy storage
• phase change material
• emissions

Acknowledgments

Authors are thankful to Government College of Engineering Pune and Karad for providing the necessary test facility and funding from TEQIPIII project.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

Cp	=	specific heat (kJ/kg-K)
CO	=	Carbon monoxide (% vol)
HC	=	Hydrocarbon (ppm)
m	=	mass flow rate (kg/s)
NOx	=	Nitrogen oxide (ppm)
Q	=	Heat transfer rate (W)
T	=	Temperature (0 C)
D	=	Diameter (mm)

Greek symbols

ρ	=	:Density (kg/m3)
$\sigma$	=	Surface Tension (N/m)
Ѵ	=	Kinematic viscosity (m2/s)
∆H	=	Latent Heat (kJ/kg)
Ƞ	=	Efficiency (%)
€	=	Effectiveness
λ	=	Excess-air factor

Subscripts

a	=	air
amb	=	ambient
avg	=	average
crit	=	critical
f	=	fluid
g	=	gas
gen	=	generated
i	=	initial
in	=	inlet
l	=	liquid
out	=	outlet
p	=	final
s	=	solid
th	=	thermal
v	=	vapour
x	=	variable

Abbreviations

A/F	=	Air to fuel ratio
Bo	=	Bond number
CC	=	Catalytic converter
ce	=	conversion efficiency
CHS	=	Chemical heat storage
Eo	=	Eotvos number
IC	=	Internal Combustion
LF	=	liquid Fraction
PCM	=	Phase change material
P	=	Physical parameter
R	=	Random uncertainty
S	=	Systematic uncertainty
TES	=	Thermal energy storage

Additional information

Funding

The work was supported by the Technical Education Quality Improvement Program (TEQIP III) .