High temperature drying of sawn timber—A review

Figures & data

Figure 1. HTD review flow.

Figure 2. The general regimes in a generic drying schedule: (1) heating, (2) capillary, (3) transition, (4) diffusion, (5) conditioning, and (6) cooling.

Table 1. Literature records of implementation of HTD and drying time differences.

References	Wood species	DBT (°C)	WBT (°C)	Initial MC (%)	Final MC (%)	Drying time (h)	Thickness (mm)
Frühwald 2007^[^27^]	Norway spruce (Picea abies)	80	N/A	Green	11.5	24	20
		120			12.2	4.5
		170			12.8	1.2
	European larch (Larix decidua)	80		Green	10.8	40	20
		120				8
		170				2.1
	Siberian larch (Larix sibirica)	80		Green	12	52	20
		120				8.5
		170				2.2
Konopka et al. 2015^[^28^]	Scots pine (Pinus sylvestris)	60	50	121.1	5.42	6	20
		80	66	113	1.73	5.5
		100	87	112.5	0.79	4
		120	99	117	0.06	3
Schneider 1981^[^29^]	Norway spruce (Picea abies)	150	95	70	8	2.2	30
		130				3.6
		110				15.4
Borrega et al. 2010^[^30^]	Norway spruce (Picea abies)	80	N/A	30	5	6.5	20
		120				2
		130				1.5
Hansson et al. 2003^[^31^]	Norway spruce (Picea abies)	60	49	Green	8	74	12
		100	91			31
Kerr 1996^[^32^]	Radiata pine (Pinus radiata)	80	N/A	Green	6	120	50
		140			2	20
McNaught 1996^[^24^]	Splash pine (Pinus elliottii)	200	N/A	Green	13	6	40
		80			10	16
Koch et al. 1976^[^21^]	Southern pine (Longleaf pine)	148	87	97.4	6	10	45
		80	71		10.6	120
McCurdy 2006^[^33^]	Radiata pine (Pinus radiata)	70	60	Green	N/A	120	50
		90	60			56
		120	70			20
		140	90			14
Cai et al. 2010^[^22^]	Sub alpine fir (Abies lasiocarpa)	120	96	89	16.2	43	38
		110		56.6	13	59
Deutschlander 2006^[^34^]	Grand fir (Abies grandis)	120	120	Green	12.9	21.1	50.8
		88–104	88–74		12.4	42
		82	77–63		16.1	50.1
Boone et al. 1989^[^35^]	American elm (Ulmus americana)	110	82	100	8.4	41	27
		82	54		7.6	150
	Sweetgum (Liquidambar styraciflua)	110	82	101	10.1	41
		82	54		6.2	126
Klement et al. 2016^[^36^]	Beech (Fagus sylvatica)	130	100	69	12.6	30	25
		150			10
		130		66	12.2	33	32
		150		70	9.4
Ananias et al. 2012^[^37^]	Radiata pine (Pinus radiata)	120	N/A	145	10	3	17
		100				18	25
		90				14
Garrahan et al. 2011^[^38^]	White spruce (Picea glauca)	160		42.4	6.1	7.5	42
		90		49.1	9.6	69
	Lodgepole pine (Pinus contorta)	160		64.9	12	4.3	42
		90		63	13.8	50
Yamsaengsung et al. 2011^[^39^]	Rubber wood (Hevea brasiliensis)	105	N/A	95	15	64	25
		80				168
Thiam et al. 2002^[^40^]	Western hemlock (Tsuga heterophylla)	116	90	Green	15.5	46	42
		82	66		15.2	23
Cai et al. 2008^[^41^]	Scots pine (Pinus sylvestris)	88	79	Green	10	34	45
		105	88			13
Chanpet et al. 2020^[^42^]	Rubber wood (Hevea brasiliensis)	60	34	115	18	64	20
		100	71			34
Theppaya et al. 2004^[^43^]	Rubber wood (Hevea brasiliensis)	90	35	60	12	16	25
		110	43	100	14	12
Cech et al. 1984^[^23^]	Norway spruce (Picea abies)	115	N/A	Green	16	24	38
Koch 1976^[^44^]	Radiata pine (Pinus radiata)	145	N/A	Green	4.7	72	11
		85			4.4	1.5
Gilmore 1976^[^45^]	Southern yellow pine (Pinus palustris)	82	N/A	85	9	41	50
		110			9.3	85
Troxell and Luza 1972^[^46^]	Lodgepole pine (Pinus contorta)	76	93	53	10.9	94	25
		104			12.1	48
Khamtree et al. 2019^[^47^]	Rubber wood (Hevea brasiliensis)	80	40	66.7	12.7	60	25
		100	60	58.3	12.2	45
		120	80	64.3	10.1	40
Baranski 2018^[^48^]	Norway spruce (Picea abies)	80	N/A	37.3	10.6	140	70
		105			15.8	430
	Beech (Fagus sylvatica)	80		80.3	7.4	85
		105			7.6	300
Milota et al. 2000^[^49^]	Hemlock fir (Abies grandis)	82	65	87	10.2	50	40
		115	82	91	13	23
		124	87	90	11.3	16
		132	98	88	10.4	14
Bovornsethanan 2007^[^50^]	Rubber wood (Hevea brasiliensis)	110	99	40	10	35	30
		120		38	9.7	25
Basilico et al. 1990^[^51^]	Beech (Fagus sylvatica)	130	N/A	64	24	5.45	27
		120		57	23	8.5
	Poplar (Populus nigra)	160		120	7	5.5	27
		140			9	6
	Douglas fir (Pseudotsuga menziesii)	160		60	14	3	27
		160		90	7	6.5	38
		104		100	12	8.5
		130		50	17	11	65
		150		70	7	2.5	18

Some data was not available (N/A).

Table 2. VOC emission of HTD.

Wood species	DBT (°C)	Thickness (mm)	VOC (mg/kg odw)	References
Southern pine	82	50	891	Ingram et al. 1996^[^74^]
	118		1110
Southern pine SW	100	50	480	Ingram et al. 2000^[^69^]
	120		440
	155		740
Southern pine with knots	100		2100
	120		3700
	155		12000
Radiata pine	120	35	200	McDonald et al. 1995^[^75^]
	140		400
Scots pine	60	60	240	Englund et al. 2000^[^76^]
	110		170
Norway spruce	60		90
	110		60
Douglas fir	71	50	700	Wu et al. 1999^[^68^]
	94		840
White fir	82	50	49	Milota 2003^[^77^]
	115		101
Southern pine	116	50	525	Milota 2006^[^78^]
Lodgepole pine			197
Western hemlock	82	50	77	Milota et al. 2006^[^79^]
	103		63
Radiata pine SW	120	30	680	Dahlen et al. 2010^[^80^]
Radiata pine HW			504

A VOC unit is a milligram per kg of oven-dried wood.

Table 3. Tangential to radial shrinkage ratio of HTD.

Wood species	Drying temperature (°C)	T/R (%)	References
Rubber wood	60	1.64	Sik et al. 2010^[^107^]
	130	1.23
Western hemlock	65	1.53	Espenas et al. 1971^[^109^]
	110	1.48
Douglas fir	65	1.92
	110	1.85
Radiata pine	40	1.55	Diaz et al. 2017^[^110^]
	100	1.47

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